CHROMOPROTEIDS

From Big Medical Encyclopedia

HROMOPROTEYDY (Greek chroma color, coloring - f-proteids; a synonym


chromoproteins) — complex proteins, molecules to-rykh contain the nonprotein prosthetic chromophoric groups absorbing light of a certain wavelength in a visible part of a range and reporting to all connection the corresponding coloring. Chromoproteids are the major pigments (see), eurysynusic in wildlife and carrying out in an organism the most various biol. functions:



Fig. Scheme of classification of chromoproteids by a functional sign.


transfer and deposition of oxygen and carbon dioxide gas, participation in tissue respiration (see biological oxidation), in redoxreactions (see), photosynthesis (see), in mechanisms of sight (see). Genetically caused disturbance of exchange of some chromoproteids is the reason of serious hereditary diseases (see), for example hemoglobinopathies (see), diseases nervous and muscular sistvkhm, the tsitokhrom connected with deficit (see), etc.

Classification of chromoproteids by a functional sign is given in a skhekhm (fig).

Respiratory pigments (see) — the oxygen carriers containing or free of gems — complex compound of protoporphyrin with iron belong to the chief representatives of lame proteids


(see Hemoglobin). Hemoproteins or proteids performing similar functions containing copper, hemocyanins are found in all organisms except for anaerobic clostridiums and lactic-acid bacteriums. With a high partial pressure of oxygen hemoproteins reversibly connect it and give in process of decrease in partial pressure of oxygen. The identical type of laying of a poly-


peptide chain around relatives on structure of the prosthetic groups containing an ion of metal, and lack of change of valency of an ion of metal at oxygenation is characteristic of them. In the oksidazny systems, hydroxylases and oxygenases participating in terminal oxidation, hemoproteins activate oxygen due to oxidation of the iron which is contained in gem, facilitating thereby interaction of oxygen with hydrogen of substrates of breath. There are other chromoproteids containing iron (see) not in structure gem; they also carry out functions of transport and deposition of the substances connected by iron. Transferrin, concentration to-rogo in blood belong to such chromoproteids reaches 2 g/l, a red-brown water-soluble chromoproteid ferritin (see), the hemosiderin consisting of several molecules of ferritin,


lactoferrin — red iron-binding protein of milk and konal-bumin — protein of eggs, similar to transferrin.

Coloring of chromoproteids of yellow color — yellow enzymes (see), their recovery and oxidation are caused by existence in a molecule of these chromoproteids as chromophore of an izoalloksazinovy ring (izoalloksazil) of Riboflavinum (see). The oxidized forms of the respiratory enzymes (see) relating to chromoproteids have red, brown or green coloring, and the majority of the chromoproteids containing copper (see) is painted in bright blue color. Coloring of chromoproteids amplifies at formation of complex connections with protein due to coordination with one or several sulfur atoms of a polypeptide chain of methionine (see). Cupriferous squirrels, thanks to ability of copper to be exposed to reversible redox — participate in nek-ry redoxreactions as one-electron carriers. Treat such squirrels stellatsianin — glikozaminoproteo-glycane from the Japanese varnish tree, plastotsianin green plants, logging in photosynthesis, azurines — low-molecular bacterial carriers of electrons. The most part of cupriferous enzymes catalyzes oxidation of organic substrates oxygen with formation of hydrogen peroxide (see); treat them a galaktozook-sidaz (KF 1.1.3.9), the dark green shade of this enzyme is connected with presence in enzyme - a substrate complex of a galactose and oxygen, a tyrosinase (KF 4.1.99.2) participating in synthesis of dioxyphenylalanine (see) and formation of melanin (see).

From juice of the Japanese varnish tree and a mushroom of Polyporus enzyme laccase is emitted (a polifenoloksidaza; KF 1.14.18.1). Reaction product, catalyzed by this enzyme, water is. Enzyme is not sensitive to SO carbon oxide and contains three types of copper ions. Copper ions of one type have blue color, they connect oxygen, ions of other type (uncolored) participate in binding of anions, stabilizing thereby the hydrogen peroxide which is formed at an intermediate stage of enzymatic reaction. The third type of the copper ions which are contained in laccase forms the two-electronic acceptor transferring electrons to oxygen with transient formation of hydrogen peroxide.

Regulation of a copper content in a human body and animals is carried out by ceruloplasmin (see Blood), to-ry on enzymatic properties reminds laccase and can participate in oxidation of bivalent iron at a stage of its accession to transferrin. The group of the chromoproteids called by superoxide dismutases prevents transformation superoxidic radical anion in a cytotoxic hydroxylic radical (see Radicals free). In addition to atom of copper in a molecule of a superoxide scavenger (peroxide-dismutase; KF 1.15.1.1) can be present zinc (see), manganese (see) or iron. In cells of colibacillus the ferriferous superoxide scavenger is found; marganetssoderzhashchy enzymes are found in mitochondrions of mammals and at nek-ry bacteria.

Properties of photosensitizers chromoproteids rhodopsin (see), a chlorophyll (see), backteriochlorophyll, carotinoids have (see) and blue or red fikobilina. Carotinoids and fikobilina as well as a chlorophyll, is receptors of energy of light radiation, however they use that part of a visible range, to-ruyu do not absorb a chlorophyll; these chromoproteids do not contain metal and their coloring is caused by existence of a polinenasy-shchenny carbon skeleton. Carotinoids protect a chlorophyll from disintegration in the presence of molecular oxygen. Contrary to a chlorophyll of a fikobilina do not contain magnesium, their prosthetic group is presented tetrapirroly with an open chain, they easily form difficult complexes with proteins — phycoerythrin and phycocyanin. These complexes log in photosynthesis of red and blue-green seaweed. Existence of fikobilin in chromatophores of seaweed (along with a chlorophyll) is considered as adaptation, with the help to-rogo the best provision of energy of light radiation of those species of seaweed is reached, to-rye exist in the conditions of insufficient lighting. It is possible to carry to chromoproteids also melanoproteida, colorants of skin, hair and wool (melanina are their part) and a brown-green pigment of an armor of Crustacea, from to-rogo during the heating the red carotinoid and stations is formed.

In a human body and animals gemsoderzhashchy chromoproteids participate in all stages of utilization of oxygen, beginning from its transport — hemoglobin, a myoglobin (see) — and finishing terminal oxidation in mitochondrions — tsitokhroma, cytochrome oxydase (see Tsitokhroma).

The biochemical polymorphism of hemoglobin which is expressed existence in erythrocytes of abnormal haemo globins is clinically shown by the hemoglobinopathies (see) proceeding most often with hemolitic anemia (see). Carry to hemoglobinopathies also cases of the hidden carriage of abnormal haemo globins or genes of a thalassemia (see). Determination of content of a myoglobin in blood and urine is used as additional diagnostic test at diagnosis of the nek-ry heart diseases, vessels and skeletal muscles which are followed by disturbance of exchange of this chromoproteid therefore the myoglobinuria develops (see). Activity of cytochrome oxydase, the enzyme sensitive to action of cyanic connections and carbon oxide, serves as criterion of weight of poisoning with these substances in blood serum (see Poisonings). Gemsoderzhashchy enzymes a catalase (see) and peroxide for (see Peroxide elements) participate in decomposition toxic for the organism of hydrogen peroxide and hydroperoxides which are formed as a result of a number of the enzymatic reactions and having the damaging effect on cellular components. Assume that at a hereditary akatalaziya (see) there is strengthening of oxidation of hemoglobin of blood to a methemoglobin and change of pussycats-lorodtransportnoy of function of blood.

Functioning of a chain of microsomes-nogo of a hydroxylation of steroids (see), fatty acids (see), aromatic compounds (see. Organic compounds) and medicinal substances it is accompanied by action of tsitokhrom of and R-450, and also the yellow enzymes accelerating recovery of a carrier of oxidation-reduction equivalents at the expense of NAD(F)» N. As such carrier the ferrodoksin proteins containing iron not in structure a subject, napr, adrenotoxin from bark of adrenal glands can act.

At alimentary insufficiency of iron or after massive blood loss decrease in concentration of hemoglobin and other gemsoderzhashchy chromoproteids is observed. Transfer of iron in fabric is regulated by the content of transferrin in blood serum. The excess amount of iron at the low content of the corresponding transport protein leads to adjournment of iron in fabrics in the form of metabolic inactive hemosiderin (see the Hemosiderosis).

Ceruloplasmin (KF 1.16.3.1) — a cupriferous oxidase, catalyzing oxidation of polyphenols, polyamines, ascorbic to - you, at the same time take part in transport of copper. At insufficiency of ceruloplasmin copper can collect in fabrics that is observed at hepatocerebral dystrophy

(see). The main diagnostic character of this disease is low activity of ceruloplasmin in blood serum. At decrease in content in blood serum of albumine and not conjugated (indirect) bilirubin it accepts the blue shade caused by presence of ceruloplasmin. Alimentary insufficiency of copper causes decrease of the activity of other cupriferous enzyme — superoxide dismutases. It increases sensitivity of an animal organism to the damaging action of active forms of oxygen, and also UF-and ionizing radiation.

At genetically caused decrease of the activity glutathione-reductase (KF 1.6.4.2), preventing an oxidizing catabolism of hemoglobin by recovery of glutathione (see), also decreases resistance of an organism to the increased concentration of oxygen.

Insufficient activity of a tyrosinase or blocking of its activity in melanocytes causes a depigmentation of skin (see Albinism).

Bibliography: Verbolovich P. A. and

Uteshev A. B., Iron in an animal organism, Alma-Ata, 1967; In both l to and nanosecond about N of. The principles and methods of diagnostic enzymology, the lane with English, M., 1981; Dickson M. and At e E. Enzymes, the lane with English, t. 1 — 3, M., 1982; M e c-l e r D. Biokhimiya, the lane with English, t. 1 — 3, M., 1980; McGilvery R. W. Biochemistry, Philadelphia, 1970.

P. A. Verbolovich, V. P. Verbolovich.

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