title: [Malate oxidation by mitochondrial succinate:ubiquinone-reductase].
abstract: Succinate:ubiquinone reductase was shown to catalyze the oxidation of L- and D-stereoisomers of malate by artificial electron acceptors and ubiquinone. The rate of malate oxidation by succinate:ubiquinone reductase is by two orders of magnitude lower than that for the natural substrate--succinate. The values of kinetic constants for the oxidation of D- and L-stereoisomers of malate are equal to: V infinity = 0.1 mumol/min/mg protein, Km = 2 mM and V infinity = 0.05 mumol/min/mg protein, Km = 2 mM, respectively. The malate dehydrogenase activity is fully inhibited by the inhibitors of the dicarboxylate-binding site of the enzyme, i.e., N-ethylmaleimide and malonate and is practically insensitive to carboxin, a specific inhibitor of the ubiquinone-binding center. The enol form of oxaloacetate was shown to be the product of malate oxidation by succinate:ubiquinone reductase. The kinetics of inhibition of the enzyme activity by the ketone and enol forms of oxaloacetate was studied. Both forms of oxaloacetate effectively inhibit the succinate:ubiquinone reductase reaction.
authors.forename: Iu O
authors.initials: IuO
authors.lastname: Belikova
authors.forename: A B
authors.initials: AB
authors.lastname: Kotliar
mesh_terms: D000818:Animals; D001665:Binding Sites; D002384:Catalysis; D002417:Cattle; D042963:Electron Transport Complex II; D066298:In Vitro Techniques; D007700:Kinetics; D008293:Malates / Q000378:metabolism*; D008928:Mitochondria / Q000201:enzymology*; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010071:Oxaloacetates / Q000378:metabolism; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013385:Succinate Dehydrogenase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013552:Swine
chemical_list: D008293:Malates; D009097:Multienzyme Complexes; D010071:Oxaloacetates; C030298:malic acid; D010088:Oxidoreductases; D042963:Electron Transport Complex II; D013385:Succinate Dehydrogenase
vernacular_title: Okislenie malata mitokhondrial'noĭ suktsinat:ubikhinon-reduktazoĭ.