From Big Medical Encyclopedia

DIAMINOXIDASE (histaminase; KF — the enzyme of a class of oxidoreductases relating to that their group of edge uses molecular oxygen and catalyzes oxidizing deamination of diamines and a histamine with formation of the corresponding aldehydes, ammonia and hydrogen peroxide; activity of this enzyme serves as the additional test in diagnosis of pregnancy and a row patol, processes. Biol. value D. in an organism of animals and the person is defined by its role in the course of neutralization of the biogenic diamines arriving from intestines, especially as a result of ichorization of proteins (at enterita, coloenterites), or the amino acids which are formed in fabrics in the course of decarboxylation (see. Decarboxylation ).

The reaction catalyzed by D. proceeds according to the equation:

R-CH 2 - NH 2 + O 2 + H 2 >O-R-CHO +NH 3 + H 2 O 2 .

For the first time the enzyme splitting histamine (see), Yustisom was open in 1915 (A. S. Eustis) in a liver of a buzzard. Best (S. N. of Best) in 1929 the enzyme inactivating a histamine found in tissue of kidneys and in a mucous membrane of intestines of animals and called it a histaminase. Later in tissues of animals D. oxidizing diamines — putrestsin, pentamethylenediamine, etc. was found. On the basis of D. given about substrate specificity and a histaminase, character of their inhibitors and activators identity of these enzymes was proved.

It is eurysynusic in the nature and found in microorganisms, the higher plants, birds and mammals. At animal D. contains almost in all fabrics, but its richest source are the mucous membrane of intestines and a bast layer of kidneys of a pig. At the person the highest activity of D. is found in tissue of kidneys, a liver, lungs, adrenal glands, a pancreas, a prostate gland, a mucous membrane of intestines, in seed bubbles and semen.

Oxidizes a histamine and the free or replaced primary diamines and does not affect the monoamines, secondary and tertiary diakhmina which are substrates for monaminoksidaza (see). Contrary to MAO it is highly sensitive to effect of hydroxylamine, semicarbazide of aminoguanidine and other inhibitors which are specifically influencing carbonyl groups of enzymes. In a blood plasma of the person and animals, and also in sprouts of bean plants and the group of aminoxidases (a sperminaminoksidaza, benzylaminoxidase) which like D. are inhibited by carbonyl reagents is found in microorganisms. On substrate specificity these aminoxidases considerably differ from D. and are close to MAO. An optimum pH value for D. at 37 ° from 6,8 to 7,6. Active groups D. of animals are piridoksal-5 '-the phosphate and bivalent copper covalently connected among themselves and protein.

D.'s activity is measured by amount of the spent substrate (histamine), by amount of the oxygen absorbed in the course of reaction and also by amount of the formed aldehydes, ammonia and hydrogen peroxide. At animals D.'s maintenance increases in kidneys and a mucous membrane of intestines after subcutaneous injections of a histamine. D.'s activity in blood can sharply increase at toxicoses of pregnancy (especially at an eclampsia). Decrease of the activity of D. in blood serum was noted at an acute anaphylaxis, bronchial asthma, hay fever and other allergic states. D.'s activity in blood serum is defined for the purpose of diagnosis of pregnancy.

See also Oksireduktaza

Bibliography: Braunstein A. E. Biochemistry of amino-acid exchange, page. From, etc., M., 1949; Zbareky B. I., Ivanov I. I. and Mardashev G. P. Extra logical chemistry, M., 1972; Lenindzher A. Biochemistry, the lane with English, M., 1976; E.A. Zeller Diamine oxidases, in book; The enzymes, ed. by P. D. Boyer a. o., v. 8, p. 313, N. Y. — L., 1963, bibliogr.

E. V. Goryachenkova.