GLYCINE

From Big Medical Encyclopedia

GLYCINE (glycine) — the aminoacetic acid, CH 2 (NH 2 ) COOH, is a part of the majority of proteins.

Is in an organism of animals and the person a source of many biologically important substances. G.'s maintenance is especially big in fibrous proteins (in collagen — apprx. 25%, in fibroin of silk — apprx. 40%); globular proteins are characterized by rather low maintenance of G. or its total absence. In fabrics and biol, liquids G. contains also in a free look and in the form of a number of derivatives among which tripeptide, gamma glutaminil-tsisteinil-glycine is especially important, or glutathione (see).

The blood plasma of the person contains apprx. 1,5 mg of % of free. Significant amounts of G. (68 — 199 mg a day) are allocated with urine. H. Braconnot in 1820 from a sulphuric acid hydrolyzate gelatin was for the first time allocated and was the first amino acid received in a crystal view from protein hydrolyzate.

G.'s crystals represent big colourless prisms, optically G. is inactive, t ° pl 290 ° (with decomposition), the Isoelectric point is at pH 6,0. In water G. we will well dissolve, has sweet taste owing to what Brakonno was called by «glue sugar».

It is easily synthesized in an organism of mammals and the person and treats replaceable amino acids. Biosynthesis of Glycine in an organism is carried out by hl. obr. from serine as a result of its interaction with tetrahydrofolic to - that (TGFK), and also from glyoxylic to - you by transamination:

G.'s catabolism can be carried out at course of these reactions in the opposite direction.

In reaction with arginine G. it transamidinirutsya, i.e. there is a transfer of amidinovy group on G. to education guanidineacetic to - you — glycocyamine (see), methylation to-rogo gives an important component muscular and other fabrics — creatine (see). It is used also in initial stages of biosynthesis of purines and purine nucleotides: The 5th '-phosphoribosyl-1-pyrophosphate in reaction with a glutamine forms 5 '-phosphoribosylamine which, reacting with G. with the participation of ATP, forms glitsinamidribotid. Of this connection after a number of its transformations it is formed inosinic to - that, edges serves as mother substance for synthesis of all purines and purine nucleotides in an organism (see. Purine bases ). An essential role is played by G. of willows synthesis porphyrines (see) of which the prosthetic group is formed hemoglobin (see) and all gemsoderzhashchy enzymes.

The increased G.'s allocation with urine (to 1 g a day) — glycinuria (see) — it is caused by an inherited disorder of the general system of transport of three amino acids (glycine, proline and oxyproline) owing to what the return absorption of these amino acids from a glomerular filtrate in renal tubules decreases. At increase in maintenance of G. in blood the risk of formation of renal oxalic stones increases (see. Urinary stones ). There are instructions also on the fact that oxarods, consisting in the increased removal with urine of oxalates and their adjournment in the form of concrements, it is connected with the disturbance of exchange of G. which is not depending on disturbance of the return absorption in renal tubules.

Determination of content of G. is usually made by methods chromatography (see) or electrophoresis (see). It is possible to determine by also specific methods, by reaction with orthophthalic dial and by coloring, to-ruyu gives with chromotropic to - that the formaldehyde which is formed at oxidation of.


Bibliography: Braunstein A. E. Biochemistry of amino-acid exchange, M., 1949, bibliogr.; Maister A. Biochemistry of amino acids, the lane with English, M., 1961; And p-s t e i n H. R. V. The metabolism of glycine, Advanc. Protein Chem., v. 9, p. 1, 1954, bibliogr.; Metabolism of amino acids and amines, Meth. Enzym., v. 17A, p. 957, N.Y. — L., 1970,

I. B. Zbareky

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