From Big Medical Encyclopedia

Nitrogen metabolism — set of chemical transformations of nitrogen-containing substances in an organism.

And. the lake includes exchange of simple and complex proteins, nucleic acids, products of their disintegration (peptides, amino acids and nucleotides) containing nitrogen of zhiropodobny substances (lipids), aminosugars, hormones, vitamins, etc.

For the normal course of processes of life activity the organism shall be provided with necessary amount of assimilable nitrogen. The major component and the main source of nitrogen of food of the person are proteic matters (see. Proteins ).

The standard daily rate of protein in food of the adult accepted in the USSR makes 100 g of protein or 16 g of protein nitrogen during the wasting of energy in 2500 kcal. However and considerably smaller amounts of protein can provide nitrogen equilibrium, i.e. a state, at Krom of amount of the entered and removed nitrogen are identical. After reception of proteinaceous food standard metabolism (see. Metabolism and energy ) raises more, than it is caused by the caloric value of protein. This phenomenon received the name «specifically dynamic action» of proteinaceous food. The mechanism of this phenomenon is not quite clear. Apparently, some amino acids — cleavage products of protein — participate in the reactions connected with hydrolysis of ATP and formation of ADF, causing the increased oxygen consumption.

At the general starvation or at insufficient nitrogenous food the quantity removed with urine and a stake of nitrogen exceeds quantity entered with food — a condition of negative nitrogenous balance. In that case when the amount of the entered nitrogen exceeds quantity of removed, there comes the condition of positive nitrogenous balance that is characteristic of the growing organism, at processes of regeneration etc.

By drawing up or assessment of a food allowance it is necessary to consider the full value of proteins which is characterized by contents in them irreplaceable amino acids, i.e. such which cannot be formed of other connections in an organism (see. Amino acids ).

The daily need of a human body for various irreplaceable amino acids is not identical (tab. 1).

Table 1. Need of the adult for irreplaceable amino acids (in per day)

{ | class = "wikitable sortable" |- ! Amino acid !! The quantity guaranteeing nitrogen equilibrium!! The minimum quantity providing nitrogen equilibrium | - | L-tryptophane | | 0,5 | | 0,25 | - | L-phenylalanine | | 2,2 | | 1,1 | - | a L-lysine | | 1,6 | | 0,8 | - | L-threonine | | 1,0 | | 0,5 | - | L-methionine | | 2,2 | | 1,1 | - | a L-leucine | | 2,2 | | 1,1 | - | L-izoleytsin | | 1,4 | | 0,7 | - | L-valine | | 1,6 | | 0,8 | }

the Proteopepsis and other nitrogen-containing substances

For high-organized vertebrate animals, including and for the person, the beginning of processes And. the lake should consider digestion in went. - kish. a path of simple and complex proteins, and also other difficult nitrogenous compounds with the subsequent absorption of products of their splitting.

The proteopepsis begins in a stomach under the influence of enzymes of pepsin (see) and gastricsin, developed in a mucous membrane of a stomach in an inactive form — in the form of zymogens (proferments).

The acid medium necessary for activation of zymogens is provided salt to - that, the mucous membrane of a greater cul-de-sac (obkladochny cells) cosecreted by glands. Pepsin (an optimum rn apprx. 2) and gastricsin (an optimum rn 3 — 4) is represented by proteases — endopeptidases which terminate peptide bonds between the amino acids located in peptide chains of a molecule of protein (see Peptidgidrolaza).

At accumulation in a stomach of the food weight possessing rather acid reaction the peloric press reflex reveals, and food weight comes in the portions to a duodenum, and then to underlying departments of a small bowel where enzymes of juice of a pancreas — trypsin participate in further splitting of peptide bonds (see), chymotrypsin (see) and carboxypeptidase (see) and enzymes of intestines — amine and dipeptidases.

Trypsin and chymotrypsin belong to endopeptidases (an optimum rn apprx. 8,0), carboxy - and aminopeptidases — to ekzopeptidaza; they split an extreme peptide bond respectively from free carboxyl and amino groups. At formation of dipeptides they are split by dipeptidases. Parallel to digestion of simple proteins in a small bowel there is a splitting of nucleoproteids, and also deoxyribonucleic (DNA) and ribonucleic (RNA) acids.

As a result of consecutive manifestation of hydrolytic activity of enzymes of digestive glands, and also microorganisms of intestines simple and complex proteins, and also other biopolymers break up, and decomposition products (low-molecular peptides, amino acids, nucleotides, nucleosides) are soaked up in a small intestine and come to blood.

In parallel there is an enzymatic disintegration of fabric proteins under the influence of fabric proteases — cathepsines (see) and peptidases (see Peptidgidrolaza). Formed shout it decomposition products also get to blood and are carried in all bodies and fabrics.

Fig. 1. The scheme of use of amino-acid fund in an organism

Fabric exchange of amino acids

the Fund of amino acids formed as a result of zymolysis of foodstuff or decomposition products of fabrics is spent for biosynthesis of proteins and many other connections inherent only to this organism, for a metabolic cost, and also for formation of the end products of a nitrogen metabolism which are subject to removal (fig. 1).

Participation of amino acids in processes of biosynthesis

Synthesis of proteins, specific to this organism, is under control of the molecules DNA which are a part of chromatin of cellular kernels.

On one of tyazhy DNA (in the place of its untwisting) under the law of a complementarity (see. The genetic code) occurs assembly (synthesis) information, or matrix, RNA (MRNK).

The transport RNA (TRNK) bearing on themselves previously activated amino acids which are fixed on MRNK approach MRNK fixed on ribosomes. Such amino acids which in synthesizable protein shall be connected by a peptide bond are located with a row, than specific primary structure of proteins with strictly certain order of the amino acids following one after another is provided.

In turn primary structure predetermines if not completely, then considerably, spatial configuration, or tertiary structure, proteins, including and proteins-enzymes.

Loss or disturbance of any link in complex process of biosynthesis of the enzyme which is carrying out a certain reaction in a metabolism can lead to heavy pathological disturbances. So, (see) loss of synthesis only of one protein-enzyme (e.g., hydroxylases is the reason of many hereditary diseases at a phenyl-pyruvic oligophrenia); «mistake» in primary structure At α-or β-chains of hemoglobin, consisting in replacement only with one of 287 amino acids, leads to formation of pathological forms of hemoglobin with the broken function of accession and return of oxygen.

The fund of amino acids is used also at synthesis of other connections.

E.g., biosynthesis of purine nucleotides (see. Purine bases ), beginning with ribosyl-5-phosphate, passes through numerous stages and comes to the end with education inosinic to - you (inosinic to - that then can be exposed to turning into adenylic and guanylic acids). At the same time participation of a glutamine (amide glutaminic to - you) as a source of nitrogen in the 3rd and 9th provisions, glycine — in the 7th situation and carbon — in the 4th and 5th provisions is required. Asparaginic to - that is a source of nitrogen in the 1st situation:

Carbon atoms (2nd and 8th) delivers formylation derivative tetrahydrofolic to - you, and, at last, carbon on the 6th place of a ring of purine undertakes from bicarbonate. These data are submitted on the scheme:

At the subsequent education adenylic to - you (see. Adenozinfosforny acids ) again it is involved asparaginic to - that, nitrogen a cut provides the amino group standing at the 6th carbon atom of a purine ring. At synthesis of guanylic acid (see) an amino group at the 2nd carbon atom undertakes from a glutamine.

Synthesis of pyrimidines begins with formation of high-energy connection — carboamylphosphate:

from ammonia (NH3), bicarbonate (NSO3-), adenosinetriphosphate (ATP) as energy source and, at last, N-atsetilglutaminovoy to - you as the activator:

The carbamile group of carboamylphosphate is enzymatically had on asparaginic to - that. Through formed carboamylasparaginic to - those, dihydroorotic and orotovy acids (fig. 2) it is formed orotidilovy to - that, passing in uridilovy to - that and uridinetriphosphate (UTF). By amination of UTF cytidinetriphosphate (TsTF) is formed, and this last reaction represents adjustable process under the law of a feed-back: TsTF slows down education carboamylasparaginic to - you, and ATP removes this braking. Thus, formation of the pirimidinovy nucleotides which are a part of nucleic acids is regulated by a ratio of content of TsTF and ATP.

Fig. 2. Scheme of biosynthesis of the pirimidinovy bases

In addition to formation of purine and pirimidinovy nucleotides, amino acids participate in formation of many other physiologically important connections.

1. From tryptophane (α-amino-β-indolpropionovy to - you): as a result of a number of consecutive enzymatic transformations it is formed nicotinic to - that, performing function of antipellagrichesky vitamin and participating in a type of niacinamide in biosynthesis of nikotpnamidny coenzymes of NAD and NADF.

2. The elementary amino acid glycine (CH 2 NH 2 COOH), in addition to participation in formation of purines, provides all nitrogen and a number of carbon atoms at biosynthesis of the porphyrines making a structural basis of bilious pigments and a nonprotein part (prosthetic group) of ferriferous chromoproteids (see).

Glycine carries out also a role of an acceptor of amndinovy group of arginine at synthesis guanidineacetic to - you, N-metilpronzvodnoye a cut — creatine (see) is important compound - a part of skeletal muscles, heart and brain, and in the form of a fosforilirovanny product (phosphocreatinine) provides a reserve of the high-energy phosphoric connections necessary for functional activity of fabric.

3. Serine participates in formation of complex amino alcohol — the sphingosine (see Sphingosines) which is a part of sphingomyelin (see Sphingolipids) — the lipid which is especially richly presented as a part of a brain and nervous tissue. Serine participates also in synthesis of a coenzyme (see) acetylations (KOA), acylderivatives to-rogo represent an active form of fatty acids (see. Lipometabolism ), participating in various processes of biosynthesis and an oxidative breakdown.

Table 2. Some biologically important nitrogenous substances which are formed of amino acids { | class = "wikitable sortable" |- ! Amino acid!! Substance which predecessor are amino acids | - | Arginine | | Spermine, spermidine, putrestsin | - | Gistidin | | A histamine, ergotionein | - | Lizin | | Pentamethylenediamine, anabasine, coniine | - | Tirozin | | Adrenaline, noradrenaline, melanin, thyroxine, a mescaline, tyramine | - | Tryptophane | | Serotonin, an indole, skatole | } are presented In tab. 2 additional data on separate amino acids, being predecessors of some other biologically important nitrogenous compounds.

Functional groups of amino acids are widely involved in various exchange reactions of substances.

First of all it belongs to the amino groups participating in reaction of interamination (see). This reaction representing the most important way of enzymatic transformation of amino acids was opened by the Soviet biochemists A. E. Braunstein and M. G. Kritsman in 1937. It consists in reversible enzymatic transfer of a α-amino group of α-amino acid on α-carbon atom of α-ketonic acid without intermediate release of ammonia.

Not only amino groups of α-amino acids, but also amino groups of amines and ω-amino acids (((((((((can participate in the reactions of interamination catalyzed by various transaminases (e.g., β-alanine, γ-aminobutyric to - you to - you to - you))); can accept amino groups not only α-ketonic acids, but also aldehydes (e.g., low-new or amber semi-aldehydes).

The general scheme of reaction of interamination is usually represented in the following look: The indispensable participant of a reversible test of enzymatic interamination performing coenzymatical function is pyridoxal phosphate (I), and also piridoksaminfosfat (II), both — derivatives of rat anti-acrodynia factor (pyridoxine). Pyridoxal phosphate assumes an amino group of amino acid and through modes of formation of the shiffovy bases turns in piridoksaminfosfat (II) which transmits an amino group also through intermediate stages on ketonic acid, being returned to an initial condition (I).

Dicarbonic amino acids — glutaminic and asparaginic — the most active participants of process of interamination. Under the influence of enzyme of a glutamatdegidrogenaza education glutaminic to - you from ammonia and keto-glutaric to - you is carried out. The amino group glutamiyovy to - you is widely transported with the participation of transaminases on various α-ketonic acids and aldehydes, forming new amino acids and amines. Nitrogen of ammonia is involved by this indirect way in composition of numerous nitrogenous organic matters.

In biosynthesis of a number of biologically active compounds the significant role belongs to process of methylation. Transfer of methyl group is, as a rule, carried out by amino acid — methionine in the form of the adenozilmetionin turning after return of methyl group into S-adenozilgomotsistein (fig. 3).

Fig. 3. Process flow diagram of methylation

Acceptors of methyl group are various; treat them: the lipids, transport nucleic acids containing minor (rare) components — metilirovanny nucleotides, guanidineacetic to - that, niacinamide, etc. Can be donors of methyl groups, in addition to an adenozilmetionin, also sincaline, betaines, N5 - methyltetrahydrofolic to - that, etc. (see. Methylation ).

Participation of amino acids in processes of a catabolism

One of ways of a catabolism (degradation) of amino acids is their enzymatic decarboxylation (see) leading to release of carbon dioxide gas and formation of the biogenic amines having high biological activity, e.g. a histamine from a histidine; serotonin from oxytryptophane; γ-aminobutyric to - you to - you to - you from glutaminic to - you:

H 2 N-CH 2 - CH 2 - CH 2 - COOH

tyramine from tyrosine

Decarboxylation of amino acids is catalyzed by decarboxylases (see) which coenzyme usually is pyridoxal phosphate, however the mechanism of decarboxylation of amino acids remains insufficiently found out. In a decarboxylase of a histidine coenzymatical function belongs to the rest pyroracemic to - you, the carboxyl group a cut is connected to a peptide chain of protein-enzyme kislotnoamidny communication:

The amines formed at decarboxylation of amino acids serve as substrates of oxidation for monoamine and diaminooxidases — the enzymes differing from each other not only a proteinaceous part, but also coenzymes: to a mitokhondrialysha of a monoaminooxidase (see) belong to yellow enzymes, their kofsrment — flavinadenindinukleotid. At diaminooxidases as a coenzyme serves pyridoxal phosphate. The ammonia and aldehydes which are formed at dezaminirovanip monamin undergo further transformations: neutralization of ammonia happens preferential by an ureapoiesis (see), a carbon skeleton of amines (in the form of aldehydes) is exposed to further oxidation.

Other process of degradation of L-amino acids is their oxidizing deamination (see) going with formation of ammonia and ketonic acids. This reaction proceeds in an organism of the highest animals and the person very slowly (contrary to oxidizing formation of ammonia from D-amino acids), however can quicker be carried out by an indirect way: at first at a persaminirovaniye it is formed α-glutaminic to - that to - that to - that, edges then at deamination is a source keto-glutaric to - you and ammonia. It is necessary to consider, however, that in reaction of deamination balance is displaced towards recovery education glutaminic to - you, i.e. from left to right:

Ways of formation of ammonia from amino acids remain insufficiently clear.

Recently G. of X. Bunatyan and his employees great value in the course of formation of ammonia (in particular, in c. the N of page and in a liver) is attributed to eliminating of NH2 group of the adenine which is in structure of a nikotinamidadenindpnukleotid (OVER). A product of this reaction is dezamgshonikotinamid-adeninedinucleotide (DENAD):

The subsequent amination DENAD is carried out with the participation of asparaginic to - you, proceeds with formation of an intermediate product (OVER - amber to - you) and after eliminating fumaric to - you lead to recovery of original structure OVER (fig. 4):

Fig. 4. Scheme transformation of a dezamnnonikotinamidadenindnnukleotid

Therefore, according to G. of X. To Bunatyan, deamination of α-amino acids with formation of ammonia proceeds through education asparaginic to - you by interamination, transfer of an amino group on DENAD, educations OVER and eliminating of ammonia from OVER.

In a crust. time still cannot be estimated, how widely this process is presented in an organism and what its biological value. DENAD attribute high biological activity as the factor which is easily getting both in oxidized, and in got into condition through a membrane of mitochondrions and considerably the oxidizing phosphorylation increasing power efficiency.

Formation of end products of exchange of simple proteins

the ammonia which Arose in processes of a metabolism and the nitrogen-free rest of amino acids undergo peculiar transformations. The main way of neutralization and binding of ammonia at ureotelic animals consists in the synthesis of urea proceeding in a liver and consisting of a series of consecutive enzymatic reactions. The first stage of this process consists in formation of carboamylphosphate (the same as at synthesis of the pirimidinovy bases), then the carbamile group is accepted by ornithine.

The citrulline of an endergonicheska formed at the same time reacts with asparaginic to - that. Formed arginineamber to - that is exposed to splitting: one of reaction products — fumaric to - that is joins in a cycle of tricarboxylic acids, another — arginine — hydrolytic is split by an arginase on urea and ornithine (fig. 5). The last joins in a chain of the transformations leading to an ureapoiesis again. Process is this, received the name of an ornitinovy cycle, proceeds in a liver though its separate reactions are presented also to heart, tissues of a brain, etc.

Fig. 5. Ornitinovy cycle

Thus, the nitrogen removed from an organism in the form of urea half undertakes from ammonia and half from asparaginic to - you.

Neutralization of the ammonia which is formed in an organism happens even by synthesis of amides — asparagine and a glutamine. The amide group of the last participates in synthesis of purines, nucleic acids etc.

Neutralization of ammonia at urikotelichesky animals (a reptile, a bird) is connected with formation of uric acid (see).

A nitrogen-free part of amino acids, as a rule, joins through numerous buffer stages in different stages of oxidizing transformations on a cycle of tricarboxylic acids (see. Tricarboxylic acids cycle ).

According to the scheme provided on fig. 6 the role of amino acids in providing power requests of an organism clearly comes to light. Disturbances in transformations of these or those amino acids are often genetically caused and are the reason of various diseases.

As a rule, defect in one specifically operating enzyme or in a series of enzymatic reactions is the reason of disturbances. These disturbances can arise, e.g., owing to insufficient formation or too bystry splitting of the coenzyme participating in many enzymatic processes.

Fabric exchange of nucleotides

Decomposition products of nucleoproteids and nucleic acids — nucleotides and nucleosides — undergo in bodies p fabrics various transformations.

Synthesis of DNA and RNA

Nucleotides — both purine, and pirimidinovy — participate in synthesis of nucleic acids in cellular kernels. Synthesis of DNA is carried out by enzymes — DNA polymerases for which as substrates serve dezoksiribonukleozidtrifosfata.

Synthesis of DNA is followed by release of molecules of a pyrophosphate in the quantity corresponding to number of molecules of the nukleozidtrifosfat which reacted. DNA (sample) and again synthesized polynucleotide form together dvutyazhny DNA. The scheme of this process can be presented in the following form:

Scheme of biosynthesis of DNA

The letter «d» before a symbol of a nukleo-zidtrifosfat or mononucleotides in the synthesized molecule DNA designates that nucleotides in which pentose is presented by desoxyribose, i.e. deoxyribonucleotides participate in biosynthesis. Formation of deoxyribonucleotides results from complex process of recovery of ribonucleotides at effect of protein, insensitive to heating — a tioredoksina.

The got into condition tioredoksina is formed under the influence of reductase (enzyme of the flavoproteshgovy nature), to-rogo serves as a coenzyme (NADF) recovered nikotinamidadenindpnukleotidfosfat according to the scheme:

The formed got into condition tporedoksina participates in formation of dezoksinukleotiddifosfat (DNDF) by transfer of the reducing equivalents on the nukleotiddifosfata (NDF) accepting them:

Again formed DNA and serving as the DNA template can connect on the ends under the influence of DNA-ligase enzyme and form a ring structure of DNA.

Fig. 6. A cycle of tricarboxylic acids (on Leninzhera)

Synthesis of RNA is carried out with the participation of a polinukleotidfosforilaza — the enzyme causing a reversible test of connection of nukleoziddnfosfat in the presence of ions of magnesium and initial RNA:

Scheme of biosynthesis of RNA

Educated polymer contains 3 ?-5 ?-phosphodiester bonds which are split by ribonuclease. Reaction is reversible and can be directed from right to left (towards disintegration of polymer) at increase in concentration of inorganic phosphate. Initial RNA in this case does not play a role of a template, on Krom the polynucleotide is synthesized. Most likely free IT is the group which is in a trailer nucleotide of RNA, it is necessary for accession to it of the subsequent nucleotides irrespective of the bases which are their part.

Apparently, in an intact cell the polinukleotidfosforilaza possesses function not of formation of polymer, and splitting of RNA. As for high-polymeric RNA with a certain sequence of nucleotides, education it is carried out by a RNA polymerase, cover action similar to the enzyme synthesizing DNA. The RNA polymerase is active in the presence of a DNA template, carries out synthesis of RNA from nukleozidtrifosfat and brings together them in the sequence predetermined by structure of DNA:

Scheme of synthesis of polymeric RNA

The catabolism of DNA and RNA

Degradation of DNA and RNA occurs on stages. The enzymes splitting RNA — ribonucleases — are widely presented in various animal fabrics. Under the influence of ribonucleases of double type — transferases and true gpdrolaz — also mononucleotides are formed of RNA oligo-.

The enzymes splitting DNA belong to nucleases — hydrolases; formation of oligonucleotides as with trailer 5th ?-phosphate, and the 5th ?-phosphate is result of their action. Under the influence of diesterases, specific nucleotidases, phosphorylases, phosphatases and nucleosidases there is a degradation of nucleotides to formation of the free purine and pirimndinovy bases which further transformation goes on different ways.

Purine bases — adenine and guanine — are exposed to hydrolytic deamination under the influence of enzymes of an adenase and guanaza. From adenine 6 hypoxanthine (hypoxanthine), are formed of guanine — 2,6 purinedione (xanthine). These transformations of ampnopurin can happen also without preliminary disintegration of the corresponding nucleotides and nucleosides. Hypoxanthine and xanthine are exposed to further oxidation under the influence of enzyme of a xanthineoxidase. An end product of this oxidation is 2, 6, 8-trioxypurine, or uric acid (see). At the person uric to - that to further transformations is not exposed and is a constant component of urine p an end product of exchange of purine nucleotides and purine bases. At the majority of mammals uric to - that does not represent an end product of a metabolism and passes into cordianine under the influence of enzyme of uricase.

Fig. 7. Scheme of disintegration (degradation) of purine bases

Stages of deamination and oxidation of purine bases are presented in fig. 7.

On other way there is a degradation of the pirimidinovy bases (see). The first step consists in recovery of uracil in dihydrouracil with the subsequent hydrolysis leading to education at first β-ureidopropionic to - you, and then β-alanine, NH3 and SO2 (fig. 8):

Fig. 8. Scheme of disintegration (degradation) of the pirimidinovy bases

Similar transformations of thymine lead to education β-aminoizo-maslyany to - you.

Thus, an end product of exchange of purines at the person is uric to - that, and pyrimidines — carbon dioxide gas and ammonia which can be sources of an ureapoiesis. As for β-alanine, this amino acid participates in biosynthesis of dipeptides of carnosine (see) and anserine (see), in a large number of the vertebrate animals who are contained in skeletal muscles.

Muscular tissue of the person contains only carnosine.

β-alanine is also a component pantothenic to - you and consequently, and the coenzyme A playing very important role in exchange of fatty acids, sterols and also in a cycle of tricarboxylic acids.

Regulation of processes of a nitrogen metabolism

And. the lake as well as all types of a metabolism, is regulated by a nervous system as directly, and through impact on hemadens. Major importance of nervous control And. the lake consists in its adaptation to the changing conditions of external and internal environment. Owing to this fact loss of nervous impacts on bodies and fabrics leads to heavy disturbances of their structure and function.

Thanks to very difficult and thin mechanisms of regulation And. the lake at the adult healthy person is provided relative constancy of structure of nitrogenous components of bodies, fabrics and internal environment of an organism. Surplus of the nitrogenous compounds entered with food is removed with urine and a stake, the shortcoming — is replenished from composition of tissues of body (it is not among irreplaceable connections).

As far as the composition of blood and fabrics has relative dynamic constancy, the composition of urine reflecting features of a metabolism in much bigger degree than structure of a blood plasma or whole blood is so changeable. Owing to this fact for conclusions about features And. the lake needs to know first of all qualitative and quantitative structure of the eaten food, to investigate qualitative and quantitative structure of the nitrogenous compounds allocated with urine and a stake and to compare the obtained data. Definition of features of composition of blood can give an idea of a qualitative originality of some parties And. the lake, but does not allow to draw the conclusion about its state in general. E.g., increase in content of proteins in a diet will lead to slight increase of maintenance of nonprotein nitrogenous components (residual nitrogen) of blood, but allocation of nitrogenous compounds and first of all urea with urine will be considerable is increased. Disturbance of oxidizing phosphorylation will change a ratio of content of creatine and creatinine P to blood serum a little, however the content of these connections and their ratio in urine will much more sharply change (see Creatine, the Creatinuria).

Despite all complexity and a variety of the reactions proceeding in an organism, the allocated end products of a metabolism remain for this look at this diet qualitatively more or less constant. They undergo considerable aberrations at various morbid conditions of an organism.

A radio isotope research of a nitrogen metabolism

Methodical methods of studying of separate stages of transformation of nitrogenous compounds extended considerably and enriched. The big role was played by implementation practice a research A. the lake of the organic matters containing radioactive or heavy isotopes of various elements and first of all phosphorus, carbon, sulfur, nitrogen, oxygen, hydrogen. Use of these connections allowed to monitor quite in details their transformations, the gradation of a tag from one substance to another which is coming to the end with release of isotope as a part of end products of a metabolism. In a crust. time it is possible to receive practically any marked amino acid which is taking part in processes of biosynthesis of the proteins inherent to this organism. These experiments allow to find out where and when amino acids are included proteins what substances or structures amino acids contact before are a part of a peptide chain. If amino acid glycine, marked isotope N 15 , to enter with food into an organism of an animal, a considerable part of isotope will be quickly brought out of an organism as a part of urea, other part remains in fabrics and is removed very slowly. The most part of the administered drug with isotope N 15 it is found in proteins, and a third of marked nitrogen joins in protein in the form of the remains of glycine, and other two thirds — as a part of other amino-acid remains. By means of marked connections many stages of the metabolic processes going in cells were open or specified. So, e.g., it was confirmed that amino groups pass from one amino acid to another (process of interamination).

Pathology of a nitrogen metabolism

Pathology And. the lake is shown in the form of pathology of protein synthesis and disturbances of exchange of various nitrogen-containing metabolites (amino acids, urea, ammonia, creatine and creatinine, uric to - that, etc.) circulating in blood and allocated by kidneys.

The main form of pathology of protein synthesis — proteinaceous insufficiency — comes at the ratio distortion between processes of biosynthesis and a catabolism of proteinaceous structures resulting in dominance of processes of disintegration over synthesis. The general proteinaceous insufficiency which is characterized by restriction of synthesis of many proteins (fabric., plasma, fermental), develops at their alimentary deficit — at the general malnutrition and at deficit of power components of food — carbohydrates and fats. In the latter case proteins are spent in an organism as an energy source (see the Metabolism and energy). The same mechanism of development of the general proteinaceous insufficiency takes place at disturbance of digestion of separate foodstuff in connection with pathology of the digestive device. The accelerated evacuation of food from a stomach, and also hypo - and anacid states limit hydrolysis of food proteins that complicates their further digestion. Disturbance of a proteopepsis after an extensive resection of a stomach is most expressed. Insufficient splitting of food proteins is observed also at loss of effect of enzymes of juice of a pancreas owing to obstruction or a prelum of its removing channel. At enterita and coloenterites digestion of food proteins is limited because of easing secretory and accelerations of motor function of a small bowel, and also disturbance of its vsasyvatelny ability. At a hyponutrient or food preferential phytalbumins and at disturbance of digestion of food proteins restriction of synthesis of various proteins in an organism comes not only because of a quantitative lack of amino acids, but also because of ratio distortion in the content of separate irreplaceable amino acids (imbalance). At the expressed proteinaceous insufficiency there comes the condition of negative nitrogenous balance, at Krom the amount of the nitrogen which is emitted from an organism is more, than amount of the nitrogen coming to an organism.

Disturbance of regulation of metabolism of proteinaceous structures is the reason of disorder of protein metabolism in the form of the strengthened disintegration. Easing and loss of nervous impacts on fabrics leads to disturbance of their trophicity and development of trophic ulcers. The lack of hormones of anabolic action (somatotropic hormone, insulin, sex hormones) is followed by primary weakening of biosynthesis of proteins. The lack of somatotropic hormone causes the expressed growth inhibition in children. Deficit of insulin at a noncompensated diabetes mellitus results in dominance of processes of disintegration and negative nitrogenous balance. Primary strengthening of disintegration of proteins is observed at a thyrotoxicosis, excess effect of steroid hormones of bark of adrenal glands.

Strengthening of disintegration of proteins in fabrics happens also at damages of fabrics (injuries, an inflammation, allergic alteration, ischemia, a degeneration). At the general intoxication, in particular an infectious origin, and extensive injuries of soft tissues and tubular bones dominance of disintegration in metabolism of proteinaceous structures has generalized character. The known role in it is played by the decomposition products coming from the damaged fabrics to the general circulation.

Pathology of protein metabolism, except disturbance of compliance of processes of synthesis and disintegration, concerning separate types of proteins is shown also in the form of inborn insufficiency of their biosynthesis owing to what develops, e.g. agammaglobulinemia (see), analbuminemiya (see). Pathology of exchange of proteins can be also in the form of the perverted synthesis of separate types of proteins, it is shown in formation of proteins, abnormal on the structure — some types of a hemoglobinopathy, emergence of protein to Bena-Jones (see. Bens-Jones of squirrels ), paraproteins at a multiple myeloma (see), etc.

Pathology of exchange of amino acids. Pathology of transamination in the form of insufficiency of this process arises at reduction of activity of enzymes — transaminases (see. Enzymes ), carrying out transfer of an amino group from amino acid on α-ketonic acid.......... Such disturbance takes place at alimentary hypo - or avitaminosis of B6 as B6 vitamin is a predecessor fosfopiridoksalya, and the last represents active group (coenzyme) of transaminases. Absolute alimentary insufficiency of rat anti-acrodynia factor practically does not meet. Relative insufficiency of its receipt can develop in an organism at the increased need for it, napr, at pregnancy or at considerable suppression by antibiotics and sulphamide drugs of normal intestinal microflora where rat anti-acrodynia factor in the quantity which is only partially covering daily requirement of an organism is synthesized.

Insufficiency fosfopiridoksalya in an organism can develop also owing to disturbance of the fermental systems turning B6 vitamin into its active form (metabolic avitaminosis) that can be observed, apparently, at treatment by Ftivazidum of TB patients.

Reduction of activity of transaminases can arise also owing to disturbance of synthesis of proteinaceous structures of transaminases (at proteinaceous insufficiency) or changes of their configuration (binding of functional groups Cycloserinum used at treatment of tuberculosis). Local disturbance of transamination in separate bodies arises at damage of their cellular structures, especially at a necrosis of the last. It is followed by an exit in blood of desmoenzymes and increase in blood of activity of separate transaminases which definition is used in clinic in the diagnostic purposes. Disturbance of a transaminprovaniye in the damaged bodies has at the same time complex character, it is caused not only loss of enzymes from cells, but also disturbance of their biosynthesis, including and enzymes of synthesis fosfopiridoksalya.

Change of intensity of process of transamination in an organism results also from ratio distortion of the reacting substrates. At a lack of α-ketonic acids, that can take place at oppression of a tricarbonic acid cycle (e.g., at a hypoxia, diabetes), transamination is oppressed, and at the excess of amino acids which is observed at the strengthened disintegration of proteins, transamination can be strengthened. In the latter case there can be a secondary oppression of oxidation in a tricarbonic acid cycle (see. biological oxidation , Tricarboxylic acids cycle ).

Disorder of regulation of activity of separate transaminases under the influence of hormones of a thyroid gland and bark of adrenal glands can be a factor of disturbance of transamination.

Oppression of process of deamination can come in connection with the reasons causing weakening of process of transamination since many amino acids lose the amino group in reaction of transamination with α-keto-glutaric to quicker - that to - that, than in reaction of direct oxidizing deamination. Glutaminic to - that, formed at amination α-keto-glutaric to - you to - you to - you, quicker, than all other amino acids, are exposed to oxidizing deamination with formation of ammonia. It is promoted by existence in cells of specific enzyme — the glutamatdegidrogenaza functioning with participation OVER. In a number of researches it is shown that at experimental avitaminosis of B 6 or at an inactivation fosfopiridoksalya Tubazidum the content of separate amino acids, except glutaminic, in blood increases, and the ureapoiesis in a liver decreases.

Oppression of oxidizing deamination in a liver arises also owing to weakening of biosynthesis of proteinaceous structures of the corresponding enzymes at proteinaceous insufficiency.

Weakening of oxidizing deamination is observed also at various forms of a hypoxia (hemorrhagic shock, etc.).

Are a consequence of disturbance of deamination a hyper aminoacidemia (see. Aminoacidemia ) — increase in a share of nitrogen of amino acids as a part of residual nitrogen (see. residual nitrogen ) and even general hyperazotemia and aminoaciduria (see).

Most clearly these shifts in And. lakes are observed at extensive defeats of cells of a liver, especially at a hypoxia of body when not only process of deamination of amino acids, but also process of a mochevinoobrazovaniye is broken. At the same time as a part of residual nitrogen, contents to-rogo can increase considerably, concentration of nitrogen of amino acids, and relative increases (or even absolute) the quantity of an urea nitrogen decreases (a productional hyperazotemia).

The productional hyperazotemia arises also at the morbid conditions which are followed by massive disintegration of proteins in an organism. In these conditions deamination of amino acids and a mochevinoobrazovaniye in a liver can be rather insufficient, and the content of residual nitrogen of blood will increase at the expense of free amino acids.

Increase in content of residual nitrogen happens as well at disturbance of secretory function of kidneys. However in these conditions the hyperazotemia occurs hl. obr. due to increase in blood of concentration of urea (a retentsionny hyperazotemia). A clinical form of the expressed retentsionny hyperazotemia is uraemia (see). Hyperazotemias can have also the mixed genesis at simultaneous insufficiency of function of kidneys and a liver and the strengthened disintegration of proteins. The productional hyperazotemia which is not complicated by disturbance of secretory function of kidneys leads to loss of amino acids of an organism with urine since filtering of amino acids in the glomerular device of kidneys exceeds in these conditions of a possibility of their reabsorption in tubules (see. Kidneys ). The strengthened removal of amino acids is revealed in the conditions of proteinaceous starvation at wound exhaustion, traumatic injuries of tubular bones, back and a brain, in hard cases of a burn, at infectious diseases, in a stage of a cachexia at malignant new growths, at a hyperthyroidism, Itsenko's disease — Cushing, prolonged treatment by glucocorticoids and drugs AKTG. In these cases the hyper aminoaciduria reflects relative insufficiency of processes of deamination in the basic is excessive the amino acids which are released at an albuminolysis. It is not excluded that at these states also direct oppression of processes of deamination in separate fabrics, especially in a liver can take place.

Other group of hyper aminoacidurias combines forms of disturbance of exchange of amino acids various by origin at which increase in their allocation is connected with disturbance of a reabsorption in canalicular system of kidneys.

Generalized disturbance of a reabsorption of amino acids comes at their filtering from blood not in a stand-at-ease, and in a complex with metals. It is shown that amino acids of blood easily form complexes with copper, and at the same time are brought by lead, cadmium, uranium out of an organism.

At Wilson's disease — Konovalova or a hepatolenticular degeneration (see. Hepatocerebral dystrophy ), for a cut disturbance of exchange of copper is characteristic, considerable excretion of amino acids in a complex with copper without simultaneous increase in concentration of amino nitrogen in blood is observed.

Disturbance of a renal reabsorption of amino acids takes place and at Fankoni's syndrome (see. Cystinosis ), called by some authors amine diabetes. The combination of the strengthened removal of amino acids (the amount of amino nitrogen in urine increases by 30 — 40 times) to a hyperphosphaturia and pseudo-rachitic changes in bones is characteristic of this disease. Also renal glucosuria is observed (see Diabetes renal).

Selective disturbance of a reabsorption is known concerning cystine. However cystinuria (see) usually is followed by the general disturbance of exchange of this amino acid. The congenital anomaly of exchange of cystine which is shown in sharply expressed cystinuria without increase in content of cystine in blood is described. Removal of cystine with urine reaches in these cases 400 — 800 mg a day whereas normal excretion of cystine does not exceed 80 mg. We will rather badly dissolve cystine, and increase in its excretion is followed by formation of tsistinovy stones in urinary tract.

Heavier disturbance of exchange of cystine is known under the name cystinosis (see). This disease is followed by the general aminoaciduria including a cystinuria, adjournment of crystals of cystine in elements of reticuloendothelial system; at it early death is observed.

Oppression of transformation of phenylalanine into tyrosine belongs to hereditary diseases. In blood and urine the amount of phenylalanine and a number of intermediate products of its exchange, in particular phenyl-pyruvic and alpha-toluic acids considerably increases. Clinically this disturbance of exchange is shown by considerable lag of intellectual development — a phenyl-pyruvic oligophrenia (see Fenilketonuriya). Insufficiently full transformation of phenyl-pyruvic and alpha-toluic acids in fenilatsetilglutamin — a normal end product of exchange of that part of phenylalanine, edge was not exposed to turning into tyrosine — it is revealed also at a viral hepatitis. Limited formation of a fenilatsetilglutamin in these cases is caused by primary restriction of formation of a glutamine in a liver.

Disturbance of oxidizing transformation of tyrosine into end products of its exchange (fumaric and acetoacetic acids) can be followed by accumulation of various intermediate products. So, disturbance of the first stage of this pathway (interamination with α-keto-glutaric to - that to - that)))))) leads to a gipertirozinemiya, a tyarozinuriya and a state tyrosinosis (see). This mechanism of disturbance of exchange is revealed at experimental proteinaceous insufficiency, damage of a liver by perchloromethane and an experimental leukosis at mice. In clinic similar disturbance of exchange of tyrosine is observed at patients with a leukosis and at collagenoses. Other form of disturbance of exchange of tyrosine — the alkaptonuria (see) developing at a delay of oxidizing transformation of tyrosine at a stage of homogentisic acid (see). Pathology belongs to congenital anomalies of exchange.

Disturbance of other directions in exchange of tyrosine is also connected with activation or oppression of the enzymes catalyzing reactions of its specific transformations. Transformation of tyrosine in pigments (melanin) painting skin and hair is defined by a stage of DOFA by activity of the tyrosinase representing specific cupriferous protein. Activity of a tyrosinase is regulated by melanoforny hormone of a hypophysis, synthesis to-rogo restrains adrenal hormones. At a hypoadrenalism there can be disturbances pigmental exchange (see). Albinism (see) represents the congenital anomaly of exchange of tyrosine consisting in loss of synthesis of enzyme of a tyrosinase.

The main pathway of tryptophane in an organism comes to an end with its transformation in nicotinic to - that. A number of intermediate products on this pathway of tryptophane, namely 3 oxykynurenine, xanthurenic, 3-oxyanthranilic acids and their derivatives, have at the increased concentration pathogenic properties.

Xanthurenic to - that promotes disintegration of a glycogen and hyperglycemia. At long increase in its concentration in blood at experimental animals degenerative changes in beta cells of a pancreas are observed. 3 Oxykynurenine and 3-oxyanthranilic acids can show also cancerogenic action.

Accumulation in blood of intermediate products of exchange of tryptophane happens owing to suppression of activity of a number of the enzymes functioning in a complex with derivatives of rat anti-acrodynia factors, B1, V2 and PP. Excess formation of toxic metabolites is revealed at chronic hepatitis, severe forms of a diabetes mellitus, an acute leukosis, chronic miyelo-and a lymphoid leukosis, a lymphogranulomatosis, rheumatism and a scleroderma. Disturbance of exchange of tryptophane can be revealed by means of test with loading.

Increase in concentration of creatinine in blood happens at disturbance of allocation by his kidneys, and the reduced removal increased pl its to urine, without simultaneous retention in blood, reflects disturbance of education it from creatine at pathology of exchange of the last in muscular tissue. Increase in excretion of creatinine is observed at hypofunction of a thyroid gland. Reduction of excretion of creatinine in combination with the increased removal of creatine takes place at a hyperthyroidism, a heavy current of a diabetes mellitus and especially at myopathies (a myasthenia, a miositis, a myatonia).

Amount of nitrogen uric to - you — an end product purine exchange (see) — as a part of residual nitrogen of blood from 0,1 to 3.0 mg of % fluctuate. Pathological increase in its concentration is observed at massive disintegration of cellular structures (starvation, hard muscular work, infections etc.) when strengthening of an erythrogenesis (see. Hemopoiesis ) is followed by release of kernels from reticulocytes. Removal uric to - you with urine is limited to its intensive reabsorption. Increase in concentration uric to - you in blood cause a possibility of adjournment it in cartilages, joint bags, sinews, fastion, and sometimes in kidneys, muscles and skin.

See also Hereditary diseases .

A nitrogen metabolism in the irradiated organism

the Nature of changes And. the lake generally depends on an exposure dose. At influence of high doses of ionizing radiation in an organism there is a process of pathological disintegration of proteins of bodies and fabrics which are not recovered by proteins of food that is shown in negative nitrogenous balance, especially at radiation in lethal doses.

In change And. the lake in the irradiated organism an essential role is played by the lowered absorption of amino acids walls of a small bowel, and also the increased release of nitrogen with urine in the next few days after radiation injury. So, e.g., at total influence by the gamma radiation and neutrons release of amino acids with urine at people increases by 10 times in comparison with norm. At radiation in high doses of experimental animals increase in content of urea in urine, tyrosine in blood, removal of amino acids with urine, a creatinuria was noted (see) that indicates strengthening of fabric disintegration. Increase in disintegration of proteins can be also result of increase in activity of proteolytic enzymes. In turn increase in activity of proteolytic enzymes is connected with a direct injury of intracellular membranes.

Changes And. lakes at radiation depend on the following main reasons: immediate effect of radiation on molecules of protein in a cell and change its physical. - chemical properties; change of biochemical mechanisms of synthesis of protein; an intensification of proteolytic enzymes in a cell; the mediated influence of radiation on activity of hemadens etc.

Change of a nitrogen metabolism in the course of aging

At advanced age significantly decreases functional capacity of a digestive tract (synthesis and secretion salt to - you, proteolytic enzymes is weakened), absorption of free amino acids in intestines is slowed down; ability of assimilation of feedstuffs at the fabric and cellular levels decreases that is connected first of all with disadaptation of fermental systems of an organism; processes of biosynthesis of proteins, nucleic acids etc. are broken.

In process of aging of an organism its ability to assimilate proteins decreases, endogenous losses of proteinaceous components of food increase that is characterized by emergence of negative nitrogenous balance.

The reasons of decrease in intensity of synthesis of protein in old age still remain not clear. Most of researchers considers that during the aging primary changes arise in regulatory genes, bringing in one cases to the accruing suppression of a transcription of separate operons (see), and to others — to temporary strengthening of biosynthesis of some proteins. At the same time biosynthesis of various proteins unevenly changes, the possible range of activation of biosynthesis is reduced, decrease in potentialitys of biosynthetic systems in the conditions of intense activity accrues quicker. In the subsequent there occur changes and in structural genes that leads to certain high-quality shifts in synthesizable proteinaceous molecules, in particular to changes in allosteric regulation of activity of enzymes.

Change of contents and activity of enzymes, conditions of proteins of cell membranes and subcellular structures leads to essential disturbance of processes of education, accumulation and use of energy in a cell that in turn leads to decrease in level of biosynthetic processes.

Characteristic example of change And. the lake during the aging is disturbance of purine exchange when in blood and fabrics a large amount of urates which are deposited then in joints and cartilages (see collects. Gout ). However so-called deposits of salts are connected not only with disturbances of purine and mineral metabolism.

There are convincing proofs that the reasons of adjournment of salts in joints and cartilages consist not only in increase in concentration of urates and calcium, and first of all in change of properties of structural proteins of connecting fabric, in particular collagen. Qualitative changes of proteins are shown by hl. obr. in disturbance of tertiary and quarternary structure of a molecule squirrel (see). At the same time the increase in durability of proteinaceous structure caused by emergence of additional, cross bonds between separate components is noted. In the course of aging physical change. - chemical properties of proteins, in particular lability, dispersion, hydrophily and electric charge of their molecules decreases. A hypothesis of domestic authors (A. A. Bogomolets, A. V. Nagorny, V. N. Nikitin) of importance for processes of aging of change physical. - chemical properties of proteins, napr, proteins of connecting fabric, their coarsening and decrease in functional activity, finds the increasing recognition in the world literature.

Numerous experimental and clinical observations of features of disbalance of processes And. lakes during the aging formed the basis for development of special diets. At the heart of the recommendations for drawing up such diets submitted on normalization of disturbances And. lakes at persons of advanced and senile age, lie: the principle of power balance of a diet with energy expenditure of an organism; providing in diets of rather high amounts of protein (1,2 — 1,3 g on 1 kg of weight) with the high content of complete animal protein (hl. obr. proteins of milk); restriction in diets of products of high concentration of purine bases (see); providing in diets of sufficient content of vitamins and microelements, in particular ascorbic to - you, Niacinum, thiamin, Riboflavinum, cobalamine, etc. that is necessary for updating of the fermental systems which are wearing out in the course of life activity.

Features of a nitrogen metabolism at children

Intensity of processes And. the lake throughout growth of the child is exposed to changes, especially pronounced at newborns and children of early age. During the first three days of life nitrogen balance is negative that has a talk insufficient intake of protein with trace amount of food. During this period tranzitorny increase in residual nitrogen in blood to 55 — 60 mg of % is found. The amount of the nitrogen emitted by kidneys increases during the first 3 days then falls and begins to increase from second week of life parallel to the increasing amount of food again.

General feature And. the lake at children — positive nitrogen balance that is a necessary condition of growth. Nitrogen of food is used by the growing organism for the plastic purposes to the maximum. So, e.g., at early stages of development of a children's organism the fermental systems providing synthesis of nucleic acids differ in the highest activity, at the same time activity of the enzymes catalyzing their disintegration is reduced.

The highest comprehensibility of nitrogen in an organism is observed at children of the first months of life. Nitrogen balance considerably decreases during 3 — 6 months of life though p remains positive.

In the second half of the year of life nitrogen balance is stabilized. According to V. F. Vedrashko (1958), at children of 2 — 3 years receiving 4 — 4,2 g/kg of protein, nitrogen balance makes 2,3 g, a retention (i.e. a delay) — 30% at a ratio of animals and phytalbumins 4:1. Children of 4 — 6 years have a satisfactory balance and a retention of nitrogen are reached during the receiving 3,5 g/kg of protein: balance of 2,7 g, a retention — 25% (V. F. Vedrashko and E. I. Arshavskaya, 1965). At children of 7 — 8 years nitrogen equilibrium is reached at introduction of 2,5 g/kg of protein: balance of 2,8 — 3 g, a retention — within 21%. By data Ying-that food of the USSR Academy of Medical Sciences, at children of 11 — 13 years at introduction of 2 g/kg of protein nitrogenous balance makes 1,8 g, a retention — 13,8%.

Indicators of a retention and nitrogen balance are subject to considerable individual fluctuations, depend on amount of protein of food, its ratio with other food ingredients. Also seasonal fluctuations of these indicators are established: they are higher in spring and summertime and are lower in the winter.

The need for irreplaceable amino acids at children is higher, than at adults, at the same time for a children's organism carry to irreplaceable amino acids also a histidine. Average sizes of need for irreplaceable amino acids, according to FAO of VOZ(1963), are presented in table 3.

Table 3. The needs for irreplaceable amino acids at children { | class = "wikitable sortable" |- ! Amino acid!! Babies (mg/kg of weight a day)! ! Children of school age (mg/kg of weight a day) | - | Gistidin | | 34 | | - | - | Izoleytsin | | 119 | | 30 | - | Leytsin | | 150 | | 45 | - | Lizin | | 103 | | 60 | - | Metionin | | 45 (In the presence of cystine) | | 27 (For lack of cystine) | - | Phenylalanine | | 90 (In the presence of tyrosine) | | 27 (For lack of tyrosine) | - | Threonine | | 87 | | 35 | - | Tryptophane | | 22 | | 7,4 | - | Valine | | 105 | | 53 | } Cells of the growing fabrics differ in high concentration of amino acids that testifies to high activity of the mechanisms providing transport of amino acids through cellular membranes. Active membrane transport of amino acids takes place in a placenta. Dent (S. E. Dent, 1948) speaks in this regard about the «placental amino-acid pump» providing the movement of amino acids from mother to a fruit (see the Placenta). It is shown that this process differs in strict stereospecificity, i.e. left-handed (L-of amino acid) pass a placental barrier with more high speed, than dextrorotatory (D-amino acids). Function of a placenta allows to explain higher content of amino acids in umbilical blood in comparison with blood of children of more advanced age and adults (tab. 4).

Table 4. Content of free amino acids in blood (in mg of %) (on Shreyera, 1965) { | class = "wikitable sortable" |- ! Amino acid!! In umbilical blood!! In blood of children!! In blood of adults | - | Alanine | | 4,8 | | 3,9 | | 3,8 | - | Arginine | | 3,3 | | 2,2 | | 2,1 | - | Glycine | | 3,4 | | 2,6 | | 2,8 | - | the Histidine | | 3,4 | | 1,8 | | 1,7 | - | Izoleytsin | | 2,3 | | 1,7 | | 1,6 | - | the Leucine | | 2,5 | | 2,3 | | 2,0 | - | the Lysine | | 8,1 | | 2,4 | | 2,8 | - | Methionine | | 0,5 | | 0,3 | | 0,35 | - | Phenylalanine | | 2,3 | | 1,6 | | 1,6 | - | Threonine | | 2,8 | | 2,3 | | 2,0 | - | Tryptophane | | 1,7 | | 0,8 | | 1,1 | - | Tyrosine | | 2,3 | | 1,6 | | 1,4 | - | Valine | | 4,9 | | 3,2 | | 3,0 | } defects of food owing to which the child receives excess of separate amino acids that serves as the reason of a delay of physical development, a hyper aminoaciduria, intoxication have Significant effect on growth of the child.

At children of early age excretion of amino acids with urine — a so-called physiological hyper aminoaciduria is raised. On the first week of life nitrogen of amino acids makes 3 — 4% of the general nitrogen of urine (on a nek-eye to data, to 10%) and only by the end of the first year of life decreases to 1%. During this period removal of amino acids per 1 kg of weight reaches sizes of removal them at the adult, the excretion of amino nitrogen reaching at newborn 10 mg/kg on the second year of life seldom exceeds 2 mg/kg. In urine of newborns the content of taurine, threonine, serine, glycine, alanine, cystine, a leucine, tyrosine, phenylalanine and lysine is increased in comparison with adults. In the first months of life in urine also ethanolamine and gomotsitrullin is found. In urine of children of the first year of life amino acids proline and hydroxyproline prevail. The functional immaturity of kidneys which is shown in an insufficient reabsorption of amino acids from a glomerular filtrate (a hyper aminoaciduria of renal type) is the reason of a physiological hyper aminoaciduria. As the proof of it serves higher clearance of amino acids. At premature, besides, the hyper aminoaciduria of reloading type since the content of free amino acids in a blood plasma is higher, than at full-term takes place.

In the course of growth of the child quantitative and qualitative characteristics change And. lake.

Still Virkhov (R. Virchow, 1856) paid attention that urine of a fruit contains surpluses uric to - you and only traces of urea. Uric to - you in renal fabric he called adjournment of crystals an urate heart attack of newborns. Researches of the major nitrogenous components of urine at children showed that a ratio uric to - you, urea of N of ammonia in the course of growth significantly change. So, the first 3 months of life are characterized by the smallest content in urine of urea and the greatest excretion uric to - you. Aged from 3 up to 6 months in urine the amount of urea increases and contents uric to - you decreases. Removal uric to - you throughout the first — the second year of life per 1 kg of weight exceed that at adults, the content of ammonia in urine in the first days of life is small, but then sharply increases and remains at a high level for all first year of life. N. F. Tolkachevskaya (1960) connects these features And. the lake with dominance at a fruit and a newborn urikotelichesky pathway of ammonia (neutralization of ammonia is provided to hl. obr. due to the strengthened education uric to - you). It is phylogenetic more ancient way which on the first year of life gradually and almost is completely forced out by ureotelic — synthesis of urea in a tricarbonic acid cycle — Genzeleyta.

Important feature And. the lake at children is physiological creatinuria (see). Creatine is found in an amniotic fluid and in urine, since the period of a neonatality and till the period of puberty. Daily excretion of creatinine increases with age, at the same time in process of increase of body weight nitrogen of creatinine as a percentage of the general nitrogen of urine decreases. The amount of the creatinine removed with urine per 1 kg of weight at children fluctuates within 5,5 — 10 mg. The sizes of daily removal of creatinine, percentage to the general nitrogen of urine received at different children of one age are close among themselves.

Bibliography: Belozersk A. N. Molecular biology — a new step of knowledge of the nature, M., 1970; Braunstein A. E. Biochemistry of amino-acid exchange, M., 1949, bibliogr.; Zbarsky B. I., Ivanov I. I. and Mardashev S. R. Biological chemistry, L., 1972; Ivanov I. I., etc. Introduction to clinical biochemistry, L., 1969, bibliogr.; Chemistry and biochemistry of nucleic acids, under the editorship of I. B. Zbarsky and S. S. Debov, L., 1968; Lehninger A. L. Biochemistry, N. Y., 1970.

Radio isotope research A. lake. — Proteins, under the editorship of G. Neyrat and K. Bailey, lane with English, t. 3, p. 2, page 594, M., 1950, bibliogr.; Haggis D., etc. Introduction to molecular biology, the lane with English, page 341, M., 1967.

Pathology And. about. — A. M. angels, etc. Influence of thyroxine on activity of some enzymes of exchange of carbohydrates and amino acids in a liver of Guinea pigs, Vopr. medical chemical, t. 17, century 2, page 165, 1971, bibliogr.; Badalyan L. O., Tabolin V. A. and Veltishchev Yu. E. Hereditary diseases at children, page 44, M., 1971; Kaplansky S. Ya. Questions of pathology of exchange of proteins and amino acids, in book: Chemical bases of processes of life activity, under the editorship of V. N. Orekhovich, page 253, M., 1962, bibliogr.; it, Pathological physiology of protein metabolism, Mnogotomn. the management on a stalemate. fiziol., under the editorship of N. N. Sirotinin, t. 2, page 455, M., 1966, bibliogr.; Kremer Yu. N. Biochemistry of proteinaceous food, Riga, 1965, bibliogr.; Lapteva N. N. Pathophysiology of protein metabolism, M., 1970, bibliogr.; Maister A. Biochemistry of amino acids, the lane with English, page 463, M., 1961; Mardashev S. R. and d river. Experience and perspectives of treatment by L-glutamine of patients with heavy epidemic hepatitis (infectious disease), in book: Usp. Hypatolum., under the editorship of E. M. Tareev and A. F. Blyuger, page 401, Riga, 1971; Repin I. S. A nitrogen metabolism at feverish states, L., 1961, bibliogr.; Horst A. Molecular pathology, the lane with polsk., page 196, M., 1967, bibliogr.

And. the lake in the irradiated organism — Buck Z. and Alexander P. Fundamentals of radiobiology, the lane with English, M., 1963, bibliogr.; Early radiation and biochemical reactions, under the editorship of E. F. Romantsev, M., 1966, bibliogr.; Shtreffer K. Radiation biochemistry, the lane with it., M., 1972.

Change And. the lake in the course of aging — The leading problems of the Soviet gerontology, under the editorship of D.F. Chebotaryov, etc., Kiev, 1972; The Leading problems of age physiology and biochemistry, under the editorship of V. N. Nikitin, M., 1966, bibliogr.; Parina E. V. Age and exchange of proteins, Kharkiv, 1967, bibliogr.; Frolkis V. V. Regulation, adaptation and aging, L., 1970, bibliogr.; Gsell D. Protein and nitrogen metabolism in the old age, Proc. 4-th int. congr. dietetics, p. 88, Stockholm, 1965; &Verz##225;r F. Aging of the collagen fiber, Int. Rev. Connect. Tissue Res., v. 2, p. 243, 1964.

And. the lake at children — Food of the healthy And sick child, under the editorship of M. I. Olevsky and Yu. K. Polteva, page 59, 212, M., 1965; Tolkachevskaya N. F. Development of processes of exchange in children of the first year of life, M., 1960, bibliogr.; Round A. F. Fiziologiya and pathology of newborn children, L., 1967; Schreier K. Eiweiβstoffwechsel, Handb. d. Kinderheilk., hrsg. v. H. Opitz u. P. Schmid, S. 57, B. u. a., 1965, Bibliogr.; Schreier K. u. a. Über die Clearance-Rate einiger Aminosäuren bei Säuglingen und Frühgeborenen, Z. Kinderheilk., Bd 79, S. 165, 1957, Bibliogr.; SereniF. Principi N. The development of enzyme systems, Pediat. Clin. N. Amer., v. 12, p. 515, 1965, bibliogr.

S.E. Severin, N. N. Lapteva; Yu. E. Veltishchev (ped.), G. I. Kozinets (I am glad.), E. F. Romantsev (I am glad. bio.), V. A. Tutelyan (mister.).