[Mechanism of interaction between quinones and 2alpha-carbanion in the active center of pyruvate decarboxylase].

The kinetics of paracatalytic inactivation of pyruvate decarboxylase by joint action of the substrate and exogenous oxidant p-benzoquinone, methyl-p-benzoquinone, 2-methyl-5-isopropyl-p-benzoquinone, trimethyl-p-benzoquinone, tetramethyl-p-benzoquinone has been investigated. Nonlinear correlation between the observed second-order rate constants and redox potentials of quinones has been found. It is supposed that negative deviations from linear dependence was caused by changing the rate determining step by the interaction of quinone with 2 alpha-carbanion in the active centre of pyruvate decarboxylase. According to structure of the oxidant the inactivation rate is limited by one electron transfer or the following protonating of the formed anion radical of quinone.