From Big Medical Encyclopedia

KARBOANGIDRAZA (carbonate dehydratase, carbonate — hydrolyase, the outdated name — coal anhydrase; KF — the enzyme catalyzing a reversible test of splitting of carbonic acid to carbonic acid and water; is one of the most widespread and most active enzymes of a human body, participates in implementation of such functions of an organism as transport of CO 2 , formation of hydrochloric acid in a stomach and maintenance of acid-base equilibrium. The size of activity To. serves as diagnostic test at a number of diseases in blood of the person.

The carbon dioxide gas which is formed in the course of tissue respiration in fabric capillaries under action To. erythrocytes passes into H 2 CO 3 (H + + HCO 3 - ); ions of H + communicate hemoglobin (see), and ions of HCO 3 - in the form of bicarbonate are transferred with blood to lungs. In pulmonary capillaries under action To. carbon dioxide gas is released from H 2 CO 3 and then is removed from an organism. To. kidneys participates in the course of a reabsorption of water in renal tubules. Decrease in its catalytic activity leads to an alkalosis of urine (i.e. to increase in values of its pH) and polyurias. To., providing maintenance of acid-base equilibrium, has significant effect on excitability and conductivity of nervous tissue. To. catalyzes also hydrolysis of a number of ethers and hydration of aldehydes. Enzyme belongs to the class LiAZ, to a subclass carbon-oxygen-liaz.

For the first time To. it is found in erythrocytes by N. Meldrum and F. J. Boughton in 1932. Activity To. is defined, except erythrocytes, in obkladochny cells of a mucous membrane of a stomach, in cells of bark of adrenal glands and kidneys, and also in cells of c. N of page, a pancreas, in a retina and lens and some other human organs.

To. mammals is metalenzyme (zinc proteid).

It is the share of 1 mol of fermental protein 1 Ghat of zinc; Zn 2+ it can be replaced on Co 2+ without change of activity of enzyme. Ions Mn 2+ , Fe 2+ and Ni 2+ are in this respect much less active.

Vegetable To. on the properties differ from To., the animals allocated from fabrics and the person.

To. erythrocytes of the person has three isoenzyme (see) — And, In and With from which the last differs in the highest activity. The ratio of these isoenzymes at various patol, states changes (normal it equally 5%, 83% and 12% respectively).

To. it is inhibited by the majority of monovalent anions, cyanide, sulfides, azides, phenols, an acetonitrile. Strong inhibitors K. animals and microorganisms some streptocides and their derivatives, napr, acetazoleamide are — Diacarbum (see) which is used in medicine as diuretic and an anticonvulsant, and also at treatment of glaucoma.

Activity To. in blood of healthy people it is quite constant, however at some patol, states it sharply changes. So, e.g., at anemias of various etiology specific activity increases To. blood, it increases and at disturbances of blood circulation of the II—III degree, and also at some damages of lungs (a bronchoectatic disease, a pneumosclerosis). At an intravascular hemolysis activity To. is defined in urine where normal it is absent * At patients with the lowered gastric acidity note low activity To. in blood, and at a hyperoxemia activity To. in blood it is a little increased.

Measurement of activity To. it is recommended to make at operative measures on lungs and heart since it can serve as an indicator of adaptation opportunities of an organism.

In view of wide use in clinic pharmakol, the drugs which are inhibitors K. (hypothiazid, Diacarbum, etc.), expediency of systematic control of activity is obvious To. in blood of the patients accepting such drugs.

Activity To. in a wedge, laboratories define by means of Brinkman's method (see. Brinkmana method ) in modification of E. M. Kreps and E. Yu. Chenykayeva, and also A. A. Pokrovsky and V. A. Tutelyan's micro method based on measurement of time necessary for shift of pH with 9,0 to 6,3 as a result of hydration of CO 2 under action To. the studied blood sample. Normal activity To., determined by this method, it is equal 2,01 ± 0,08 units, and in terms of 1 million erythrocytes 0,458 ± 0,006 units (for 1 unit of activity To. accept acceleration of the catalyzed reaction twice in comparison with not catalyzed at reference conditions: temperature 0 — 1 °, time 100 — 110 sec., cultivation of blood 1: 1000).

Bibliography Crêpe of E. M. Respiratory enzyme — coal anhydrase and its value in physiology and pathology, Usp. sovr, biol., t. 17, century 2, page 125, 1944; L e-nindzher A. Biokhimiya, the lane with English, page 177, M., 1974; L i n d s k about g S. a. o. Carbonic anhydrase, in book: Enzymes, ed. by P. D. Boyer, v. 5, p. 587, N. Y. - L., 1971, bibliogr.; Scrutton M. Assay of enzymes of carbon dioxide metabolism, in book: Meth. microbiol., ed. by J. R. Norris a. D. W. Ribbons, v. 6A, p. 479, L. — N. Y., 1971.

G. A. Kochetov.