title: [Paracatalytic inactivation of pyruvate decarboxylase in the presence of quinones].
abstract: Pyruvate promotes the yeast pyruvate decarboxylase inactivation under the influence of substituted p-benzoquinones. Pyruvate decarboxylase activity is not renewed after the removal of low-molecular impurities by gel filtration and subsequent addition of dithiothreitol, thiamine diphosphate, magnesium chloride. The inactivation rate under joint action of 2-methyl-5-isopropyl-p-benzoquinone and pyruvate is regulated by the pseudo-first-order equation. The relationship between pseudo-first-order rate constant and pyruvate concentration takes the shape of hyperbola. The inactivation order with respect to quinone is determined by oxidant concentration and pH value. Maximum pseudo-first-order rate constant values in the presence of the excess substrate and 2-methyl-5-isopropyl-p-benzoquinone are observed at pH 5.9-6.0. The data obtained evidence for the fact that during inactivation quinone interacts with "active acetaldehyde" being the intermediate in the process of catalysis with pyruvate decarboxylase.
authors.forename: A I
authors.initials: AI
authors.lastname: Vovk
authors.forename: I V
authors.initials: IV
authors.lastname: Murav'eva
mesh_terms: D016227:Benzoquinones / Q000737:chemistry*; D002384:Catalysis; D002850:Chromatography, Gel; D003653:Decarboxylation; D006863:Hydrogen-Ion Concentration; D015394:Molecular Structure; D008970:Molecular Weight; D011767:Pyruvate Decarboxylase / Q000037:antagonists & inhibitors*; D012441:Saccharomyces cerevisiae / Q000201:enzymology
chemical_list: D016227:Benzoquinones; D011767:Pyruvate Decarboxylase; C003466:thymoquinone
vernacular_title: Parakataliticheskaia inaktivatsiia piruvatdekarboksilazy v prisutstvii khinonov.