HOLESTERINESTERAZA (synonym: xo-
of a lesterolesteraz, hydrolase of steri-new ethers, KF 184.108.40.206) — enzyme of lipidic exchange. Catalyzes a reversible test of hydrolysis (see) esters of cholesterol and higher fatty acids: ether
of cholesterol + H20 = cholesterol - f-anion of fatty acid. Considered earlier that the holesterinesteraza catalyzes both hydrolysis, and synthesis of ethers of cholesterol, however now it is possible to believe established that synthesis of cholesteric ethers proceeds under the influence of special enzyme — a cholesterol-acyltransfer-zy (KF 220.127.116.11) with participation of a coenzyme A. Holesterinesteraza was for the first time found in 1910 Mr. Kohn-to (To. Kondo) in a liver. S. V. Ned-zvetsky showed that this enzyme is not identical to a lipase. Holesterinesteraza contains in a liver, a pancreas, a spleen, a mucous membrane of intestines, in kidneys, a wall of an aorta, blood serum. Tissue of a brain, the richest with cholesterol, is almost deprived of activity of a holesterinesteraza. Holesterinesteraza in a liver contains in cytoplasm of hepatocytes (most part), and also in microsomes (see) and lysosomes (see) that is characteristic also of other fabrics. The Lizosomalny holesterinesteraza, as well as the majority of other hydrolases (see) this fraction, has an optimum of pH in acid medium; the holesterinesteraza which is localized in other sites of a cell is most active at pH 6,1 — 7,5.
The reaction catalyzed by holeste-rinesterazy does not need cofactors, however salt bilious to - t
and, to a lesser extent, salts nek-ry the highest fat to - t (soap) activate enzyme. Inhibitors of a holesterinesteraza are sulphhydryl reagents (see Suljfgi-drilny groups): p-hlormerkuri-
benzoate, N-etilmaleimid, iodatse-tamid, etc. From oppression by these substances the holesterinesteraza is protected by the recovered glutathione (see).
Holesterinesteraza is not received in a high cleaning look yet, and the nature of protein of this enzyme is not established. Methods of definition of activity of a holesterinesteraza are based on use as substrates of the ethers received from cholesterol (see), marked C14 or H3. After an incubation with enzyme free marked cholesterol is separated a chromatography (see) on columns from silica gel and measure radioactivity.
Fiziol. the role of a holesterinesteraza is studied insufficiently. However it is established that the holesterinesteraza of a pancreas and intestines participates in processes of digestion of lipids (see) and absorptions of cholesterol and fatty acids (see) in intestines. Holesterinesteraza of a liver hydrolyzes the ethers of cholesterol coming to blood. However value of enzyme is not exhausted by it. Recently its possible role in a pathogeny of atherosclerosis is widely discussed (see). It was shown that inborn insufficiency of a lizosomalny holesterinesteraza of an aorta at animals leads to massive atherosclerosis, therefore, accumulation of lipids in walls of an aorta at atherosclerosis is at least partially connected with insufficient decomposition of ethers of cholesterol. At lines of rats with spontaneous hypertensia extent of decrease of the activity of a holesterinesteraza of an aorta correlated with the size of blood pressure. Introduction to such rats of antihypertensives reduced blood pressure and in parallel increased activity of a hole-sterinesteraza of an aorta.
Bibliography: Nedzvetsky S. V.
Holesteraza, its properties and synthetic action, Biochemistry, t. 2, century 5, page 758, 1937; Goodman D. S. Hydrolysis and formation of cholesterol esters in rat liver, in book: Meth. in enzymol., ed.
by S. P. Colowick a. N. O. Kaplan, v. 15, p. 522, N. Y. — L., 1969; Lands W.E.M. Lipid metabolism, Ann. Rev. Biochem., v. 34, p. 313, 1965. V. I. Rozengart.