PROLINE

From Big Medical Encyclopedia

PROLINE — pyrrolidine-2-carboxylic acid, the imino-acid which is a part of the vast majority of proteins. The item and its oxyderivative — oxyproline (hydroxyproline) are especially characteristic of proteins of connecting fabric. Genetically caused disturbance of exchange of P. and oxyproline is the reason of hereditary diseases.

Imino-acids (see), to the Crimea P. belongs, are so close on the properties to to amino acids (see) that proline and oxyproline can be considered as amino acid.

The item is among replaceable amino acids, it is synthesized in an organism from glutamic acid (see) and from ornithine (see).

L-proline has an appearance of the white powder consisting of crystals in the form of needles or prisms. Let's well dissolve in water and ethanol, it is insoluble in organic solvents; t ° pl 220 — 222 ° (with decomposition). Rigid conformation of the remains of P. influences the nature of laying of a polypeptide chain of protein during the formation of its tertiary structure.

Content of oxyproline reflects a condition of metabolism in urine collagen (see) in an organism. Excretion of oxyproline increases at some diseases, naira, at innidiation of malignant tumors in a spinal cord.

The important enzyme participating in P.'s exchange. the prolineoxidase is (pyrroline - 5 - carboxylat — reductase; KF 1.5.1.2), P. catalyzing transformation of the remains in a polypeptide chain in oxyproline. At hereditary insufficiency of a prolineoxidase free P.'s maintenance sharply increases in blood serum and P.'s removal with urine increases (normal the daily amount of urine contains about 10 mg of proline). At inborn insufficiency of an oxyprolineoxidase the content of oxyproline in blood serum strongly increases. This disturbance does not influence exchange of collagen and P. U of children with such genetically caused anomaly of exchange note the expressed mental retardation (see. Oligophrenias ).

Other enzyme participating in P.'s exchange is the prolinase (a prolylendopeptidase; KF 3.4.13.8). It represents the endopeptidase specific by the remains of proline in a polypeptide chain. The prolinase catalyzes hydrolysis of such biologically active compounds as angiotensin (see) and bradikinin (see. Mediators of allergic reactions ).

P.'s definition and oxyproline in biol, substrates is based on processing of the studied sample by sodium hypochlorite (NaClO) in alkaline condition and the subsequent definition of reaction products by means of au phthalic aldehyde. The method of definition of P. in blood serum consists in spektrofotometrichesky determination of amount of the painted reaction product P. with isatin.


Bibliography: Lenindzher A. Biochemistry, the lane with English, M., 1976; Mahler G. and Kordes Yu. Fundamentals of biological chemistry, the lane with English, M., 1970; M e D. E's c-ler. Biochemistry, the lane with English. t. 1, M., 1980; Shtraub B. Biokhimiya, the lane with Wenger., Budapest, 1965.

O. D. Lopina.

Яндекс.Метрика