[The interaction of pyruvate decarboxylase with the quinone-ferricyanide oxidative system].

Inactivation of yeast pyruvate decarboxylase in the presence of substrate and oxidative system containing substituted quinone and ferricyanide has been investigated. It was established that ferricyanide at pH 5.2-6.4 can prevent irreversible inactivation of the pyruvate decarboxylase caused by the concerted action of pyruvate and substituted quinone. The influence of ferricyanide which depends on the redox potential of the substituted quinone is decreasing in a series tetramethyl-p-benzoquinone, trimethyl-p-benzoquinone, 2-methyl-5-isopropyl-p-benzoquinone. It is supposed that the effect of the oxidative system partially converting the nonoxidative to oxidative function of pyruvate decarboxylase is attributed to the oxidation of active acetaldehyde by substituted quinone and reaction of resultant semiquinone radical with ferricyanide.