LIPOPROTEIDLIPAZA (triatsilglitseroprotein-acylhydrolase; KF 188.8.131.52) — the enzyme which is actively participating in lipidic exchange, catalyzing hydrolysis of the triglycerides which are a part of coarse-dispersion lipoproteids — chylomicrons and lipoproteids of very low density, and by that regulating concentration of triglycerides in blood. Main function L. in an organism of animals and the person its participation in supply of cells fat to-tami, i.e. substrate for oxidation energetically necessary for an organism is (see. Lipometabolism ).
Function L. in an organism it is not limited to its participation in lipidic exchange. B. A. Kudryashov carried L. to humoral agents of anticoagulative system of blood. L., forming complexes with heparin and with coarse-dispersion lipoproteids (see), gains ability to dissolve the clots of fibrin which are not stabilized by a factor of XIII.
Activity of L. in blood serum changes at some diseases that, certainly, will be used as the additional test at diagnosis of these diseases. Assume that change of activity of L. in a myocardium and a liver plays a part in a pathogeny of atherosclerosis.
For the first time action of L. observed P. F. Hahn in 1943. He found out that intravenous administration heparin (see) experimental animal (dogs) from alimentary lipemia (see) causes a bystry enlightenment of an opalescent blood plasma. However only in 1950 N. J. Anderson and Fositt (V. of Fawcett) established that intravenously entered heparin is the reason of emergence in a blood-groove of the new factor of the enzymatic nature possessing antikhilomikronemichesky action. Later it was shown that the enlightenment of a blood plasma is followed by emergence in it free fat to - by t p it is connected with hydrolysis of the triglycerides which are contained in chylomicrons. Anfinsen (S. V. of Anfinsen) suggested to call new enzyme «factor of an enlightenment». E. D. Korn found enzyme which on the action was identical to «a factor of an enlightenment» in a cardiac muscle of a rat, and called its «lipoproteidlipaz». Especially interest in L increased. after it became clear that lipoproteids of very low density have atherogenous properties.
L. it is found in many bodies and tissues of animals and the person, and also in microorganisms. In an organism of L. it is directly connected with a naruzhy cytoplasmic membrane of cells. In walls of vessels and capillaries of L. it is localized in membranes of endothelial cells of vessels and capillaries. There are data that L., coming to blood, circulates in it in the form of a complex with heparin and it is allocated in blood generally at an alimentary lipemia and at a number of the states causing reflex emission of heparin. In a blood plasma of hungry animals and people lipoproteidlipazny activity is practically absent. Activity of L. in blood appears at them after reception of greasy food or after intravenous administration of heparin or geparinopodobny substances.
L., like other hydrolases, treats, apparently, «serinovy» enzymes, i.e. contains the rest of serine in the active center. However funkts, groups of an active center of L. are not identified yet.
Optimum of action of L. from different sources usually is between pH 8,0 — 9,0. Enzyme is besieged at pH 5,0 — 5,5, and also ions of heavy metals and protaminsulfaty. Inhibitors L., unlike lipases, a pyrophosphate, diizopropilftorfosfat, saponides, salts bilious to - t, polycations and polyanions, 1 N of NaCl are. Activator L. the specific protein which is contained in lipoproteids of a blood plasma which was called apoproteidy C-II is
it is Most in detail studied post-heparin (appearing in blood after administration of heparin) L. rats. Enzyme contains about 1 mol of phospholipids on 1 mol of protein, and also small amounts sialic acids (see), neutral sugars and aminosugar. Removal of phospholipids from drug of enzyme leads to loss of enzymatic activity. Enzyme has subunit structure and there can be in the form of monomer, a dimeasure and tetramer. The most stable active form of enzyme is dimeasures, the pier. the weight (weight) to-rogo is equal to 37 000.
Activity of L. in blood serum and others biol, liquids activity is defined practically by the same methods, as lipases (see), however at the same time the substrates specific to L are used., i.e. natural chylomicrons or various activated artificial fatty emulsions. Activation of fatty emulsions consists in their incubation with fresh blood serum of the person within 30 min. at 37 °. At the same time there is a formation of stable complexes of triglycerides to lipoproteids of blood serum which on the structure are very similar to natural substrate for L. — chylomicrons.
Change of activity of L. in blood serum it is observed at the diseases which are followed by disturbance of lipidic exchange: a nephrosis, diabetes, pancreatitis, cirrhosis, giperlipoproteinemiya of I and V types (across Fredrikson), atherosclerosis.
Hyulsmann (W. Villages of Hulsmann) and Jansen (N. of Jansen) assumed that increase in activity of L. in a cardiac muscle with simultaneous decrease in its activity in a liver creates favorable conditions for development of atherosclerosis. During the modeling of atherosclerosis it was established that intravenous administration of L. leads to favorable changes of lipidic exchange and has the braking effect of a pas a depression of anticoagulative system of blood and on development of a predtrombotichesky state. These data are theoretical justification of search of the antiatherosclerotic medicines based on action
L. Insulin increases activity of L. in fatty tissue. It is possible that it is explained by stimulation of synthesis of L., but not increase in its catalytic activity. It is not excluded that concentration cyclic 3', 5 '-AMF plays a part in change of speed of synthesis of enzyme.
Bibliography: Bazazyan G. G., etc. Allocation of a lipoproteidlipaza from post-heparin plasma of rats and check of its biological activity, Vopr. medical chemical, t. 20, century 1, page 14, 1974; Brokerkhof X. and Jensen R. Lipolytic enzymes, the lane with English, page 121, M., 1978; Kudryashov B. A., B and z and z I am G. G.'s N and B about N f and t of t about L. L. Lipoproteidnaya a lipase of blood and its property as component of physiological anticoagulative system, in the same place, of t. 9, century 5, page 533, 1963; M and l ah about in and E. A. and d river. About new function of a lipoproteidlipaza in blood, Dokl. Academy of Sciences of the USSR, t. 231, No. 2, page 495, 1977; F i e 1-d i n g P. E., Shore V. G. a. Fielding of Page J. Lipoprotein lipase, properties of the enzyme isolated from post-heparin plasma, Biochemistry, v. 13, p. 4318, 1974; H ii 1 s m a n n W. C. a. Jansen H. High myocardial and low hepatic lipoprotein lipase activities responsible for the initiation of atherosclerosis, Biochem. Med., v. 13, p. 293, 1975; Porte D. W i 1 - 1 i a m s R. H. Post-heparin lipolytic activity following intravenous heparin-S33, Proc. Soc. exp. Biol. (N. Y.), v. 118, p. 639, 1965.
T. P. Levchuk.