SUCCINATEDEHYDROGENASE [KF 1. 3. 99. 1; succinate: (acceptor) oxidoreductase; synonym: suktsindegidrogenaza (ustar.) fumaratereductase] — enzyme of a class of oxidoreductases and group of the oxidoreductases operating on CH-CH - group of donors; catalyzes reaction of formation of a double bond in a molecule of substrate due to direct dehydrogenation on simple carbon — a carbon bond. Biol. S.'s role is extremely big since this enzyme catalyzes one of the main reactions of a cycle tricarboxylic to - t (see. Tricarboxylic acids a cycle), and serves as direct electron sink from the recovered S. To Q10 (ubikhinon-10). Soviet biokhimikokhm by A. D. Vinogradov it was established that the component of a mitochondrial membrane responsible for S.'s reaction with ubikhinony, is special polypeptide about a pier. it is powerful (weight) apprx. 13000. A. G. Ginetsinsky and Yu. V. Natochin showed that S. is one of components of the system providing in aerobic conditions transmembrane transfer of ions of Na + in kidneys and other osmoreguliruyushchy bodies. Measurement of activity of S. in lymphocytes is tried to be used for assessment of a condition of transplant immunity.
Biol. oxidation amber to - you (succinate) was opened in 1909 for Tunbergom (T. Thunberg). The enzyme catalyzing this oxidation, a succinatedehydrogenase — is eurysynusic in an animal and flora. At the person and the highest vertebrate animals of S. kidneys, a liver and heart are richest. It is established what in S.'s cells contains only in mitochondrions and it is localized in their inner membrane. The page represents protein about a pier. it is powerful apprx. 70 000, its molecule contains covalently the connected FAD and two (Fe2S2) - the center. This protein is closely connected with other protein (a pier. weight apprx. 27 000) having (Fe4S4) - the center, but free of flavin. Communication of FAD with protein in a molecule C. is carried out at the expense of imidazolny group of the rest of a histidine and 7-CH 3 - groups of Riboflavinum.
The village has almost absolute specificity, catalyzing oxidation of succinate in fumarating (anion fumaric to - you) according to the equation:
In very insignificant degree under the influence of S. are oxidized monokhlor-and monomethyl succinate. The page has accurately expressed optimum of action between pH 7,0 and 8,0. Among inhibitors C. first of all it is necessary to mention the connections which are specifically connecting SH groups — n-chlorine-merkuribenzoat, about-yodozobenzoat, iodacetamide, maleic to - that, ions of heavy metals, etc. It testifies to an essential role of SH-rpynn in ensuring catalytic activity of enzyme. One of the strongest inhibitors C. is malonate, to-ry is a classical example of a structural analog of substrate of enzymatic reaction, the speaker as a competitive inhibitor of enzyme. Anions of others double-base to - t (oxaloacetate, oxalate, glutarate) also suppress activity of Page.
From methods of definition of activity of S. are most widespread photometric (see. Photometry ), in to-rykh as hydrogen acceptor use substances, colourless in the oxidized form (e.g., derivatives a tetrazoliya) and the giving painted products at recovery (formazana). This reaction is the cornerstone also of histochemical identification S. Obshcheupotrebitelen the method based on recovery of a 2,6-dikhlorfenolindofenol in the presence of phenazinemetasulphate with the subsequent photometry at 600 nanometers.
Bibliography: Chaps V. G., Gavrikov E. V. and Vinogradov A. D. Reconstruction succinate-ubikhinon-reduk-taznogo of the site of a respiratory chain of mitochondrions, Biochemistry, t. 45, century 4, page 747, 1980; Zelentsova O. A., Zharkova T. G. iverbolovich V. P. Dehydrogenases of a citrate cycle of lymphocytes as an indicator of activity of transplant immunity, in book: Biochemistry and a patokhimiya of a metabolism, under the editorship of P. A. Verbolovich, page 157, Alma-Ata, 1975; Natochin Yu. V. Ionoreguliruyushchaya function of a kidney, L., 1976; In e i-n ert H. Iron-sulfur centers of the mitochondrial electron transfer system, in book: The iron-sulfur proteins, ed. by W. Loven-berg, v. 3, p. 61, N. Y., 1977; H a t e f i Y. a. S t i g a 1 1 D. L. Metall-containing fla-voprotein dehydrogenases, in book: The enzymes, ed. by P. Boyer, v. 13, p. 222, N. Y., 1976; King T. E. Preparation of succinate dehydrogenase and reconstitution of succinate oxidase, in book: Methods in enzymol., ed. by S. P. Colowick a. N. O. Kaplan, v. 10, p. 322, N. Y., 1967.
V. I. Rozengart.