CREATINE

From Big Medical Encyclopedia

CREATINE (synonym: methylglycocyamine, guanidine-methylglycine) — methyl-guanidyl-acetic acid, is one of important components of a nitrogen metabolism in an organism; collecting in fabrics in the form of vysokoergichesky fosforilirovanny derivative — creatine phosphate, To. participates also in energy balance. To. carries out a regulatory role in many biochemical, processes: stimulates biosynthesis of proteins (a creatine kinase, actin and heavy chains of a myosin), activates process of breath and oxidizing phosphorylation in mitochondrions.

creatine

The processes going in a cell with consumption of energy — reduction of muscles, active transport of ions in nervous tissue — are followed by splitting of significant amounts of creatine phosphate and accumulation To. at a fixed level or little changes of concentration of ATP.

In medicine determination of content To. and its derivative — creatinine serves in blood and urine for diagnosis of a number of diseases.

To. contains in various tissues of the person, vertebral and some species of backboneless animals. It is for the first time found by the fr. scientist Shevrel (M. E. Chevreul) in 1835 in extract from skeletal muscles.

Pier. the weight (weight) To. 131,14. To. forms the crystals with accession of one water molecule having an appearance of monoclinical prisms (a pier. weight 149,16). Let's rather badly dissolve in water (1,35 g in 100 g of water at 18 °), it is insoluble on air, very badly alcohol-soluble (0,0063 g in 100 g of cold ethanol).

In the highly acid environment K. loses a water particle and passes into creatinine by short circuit of communication between NH 2 - and COOH groups.

creatinine

This property K. it is the basis for one of methods of its quantitative definition.

Creatinine (1 - metilglikotsiamidin) is one of end products of protein metabolism at vertebrate animals and the person and constantly is present at urine. The amount of the creatinine emitted by the person in days equally on average in 0,6 — 2 g also depends on extent of development of muscles and content of creatine phosphate in it. The relation of amount of the creatinine (in mg) emitted by the person per day to body weight (in kg) carries the name of a creatinine coefficient. Usually creatinine coefficient fluctuates at men within 20 — 30, at women — 10 — 25.

In urine along with creatinine also K. U of adult healthy people contents is found To. in urine it is very small (0,05 — 0,25 g in the daily volume of urine). Allocation of significant amounts To. with urine carries the name of a creatinuria and it is observed at various patol, states, and also at children is normal (see. Creatinuria ).

In skeletal muscles of the person and vertebrate animals total quantity To. makes (in mg of %) 250 — 550; in a cardiac muscle — 150 — 300; in unstriated muscles — 50 — 100; in tissue of a brain — 100 — 150. In bodies where it is synthesized To. — kidneys, a liver, a pancreas — contents To. very low (10 — 40 mg of %). In small concentration (1 — 1,5 mg of %) To. it is found in a blood plasma of the person and animals (see. Creatinemia ).

In an organism of animals and the person To. it is synthesized from three amino acids: arginine (see), glycine (see) and methionine (see). Synthesis To. occurs in two stages. The first stage of synthesis — education guanidineacetic to - you by transfer of amidinovy group from arginine on glycine — occurs in kidneys and a pancreas with the participation of L-arginine enzyme: glycine — amidinotransferases (KF 2.6.2.1). Activity of this enzyme in a pancreas in 5 times more, than in kidneys.

The second stage of synthesis To. — reaction of methylation guanidineacetic to - you with the participation of the activated form of methionine (S-adenozilmetio-nina) happens in a liver and a pancreas. This reaction guanidineacetate-methyltransferase (KF 2.1.1.2) catalyzes enzyme.

Consider that from a liver and a pancreas To. with a blood flow comes to various bodies and fabrics (in skeletal and cordial muscles, a brain and nervous tissue).

Ways of zymolysis To. in tissues of vertebrate animals and the person are unknown. About 2% of the general contents To. in an organism daily not enzymatically turns into creatinine which is emitted with urine.

In muscular and brain fabrics with the participation of enzyme creatine kinases (see). To. reacts transphosphorylations with ATP, turning at the same time into creatine phosphate. It is the only known way of formation of creatine phosphate.

Creatine phosphate was described in 1927 by Q. P. Eggleton and Q. P. Eggleton, the Fisc (Page H. Fiske) and Y. Subbarow. In 1929. The fisc and Y. Subbarow established that this connection consists from To. and phosphoric to - you in a molar ratio 1:1.

creatine phosphate

Creatine phosphate belongs to the class phosphagens (see) — vysokoergichesky fosforilirovanny the derivatives playing a role of accumulators of energy in a cell. At fiziol, conditions the size of free energy of hydrolysis of fosfoamidinovy communication of creatine phosphate is equal to 10,3 — 10,8 kcal/mol. Creatine phosphate along with To. and by a creatine kinase it is found almost in all bodies and tissues of vertebrate animals and the person and some species of backboneless animals (erinaceouses, chordates). The greatest number of creatine phosphate is found in skeletal muscles. In 1922 by A. V. Palladin it was suggested about an important role To. in chemism of muscle performance. A. V. Palladin and it sotr. it was shown that at the training causing increase in operability of muscles the last are always enriched To. and creatine phosphate. During the weakening of function of muscles the content of creatine phosphate decreases.

It is established that creatine phosphate regulates glycolysis (see), inhibiting a fosfofruktokinaza, a pyruvatekinase and activating glyukozo-1,6-diphosphatase. See also Nitrogen metabolism .

Methods of definition of creatine in biological liquids. To. define after preliminary transfer in creatinine during the heating of the studied sample with mineral to - that. Creatinine in blood and urine is determined by Folin's method — Poppera, based on recovery by creatinine in strongly alkaline condition picric to - you in pikramovy to - that, having krasnooranzhevy color (see. Jaffe reaction ).

Definition To. make also by the method based on formation of colored compound K. with diacetyl and alpha-naphthol in alkaline condition. Definition of concentration of the painted complex is carried out colorimetric or spektrofotometrichesk at 540 nanometers.

Creatine phosphate is determined by creatinine or by phosphorus. The first method consists in decomposition of creatine phosphate on creatinine and phosphoric to - that in the presence of ammonium molybdate in acid medium and colorimetric definition of creatinine with picric to - that. The second method is based on splitting of creatine phosphate in acid medium and the subsequent definition of the formed mineral phosphate with molybdenic to - that and eykonogeny.

The spectrophotometric method of definition is more sensitive To. with a creatine kinase and two fermental systems interfaced to it — a pyruvatekinase and a lactate dehydrogenase (Tantser's method — Gilvarga). The method is based that at addition to the studied sample of ATP and a creatine kinase all endogenous To. turns into creatine phosphate and it is formed equimolar To. quantity of ADF. Concentration of the formed ADF is defined in the presence of added to a sample of a pyruvatekinase, a lactate dehydrogenase and their substrates of a spektrofotometricheska on reduction of absorption of the recovered NAD-N 2 at 340 nanometers.

By the most sensitive method of definition To. in biol, liquids the flyuorimetrichesky method based on education in alkaline condition of a complex K is. with ninhydrin, the having maximum of fluorescence at 495 nanometers. By this method K. is defined in concentration 1 • 10 - 7 M. Guanidin and some of his derivatives which usually contain in urine prevent definition K. Guanidin effectively leaves from urine during the processing by its anion-exchange resins.



Bibliography: Mardashev S. R. Biochemical problems of medicine, page 110, M., 1 975; P and l of l and d and A. V N. Chosen works, page 109, Kiev, 1975; Todorovy. Clinical laboratory trials in pediatrics, the lane with bolg., page 169, 739, Sofia, 1968; Clinical biochemistry, ed. by H. - Ch. Curtius a. M. Roth, v. 2, B. — N. Y., 1974.


L. B. Belousova.

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