Pyruvate: Ferredoxin oxidoreductase: II. Characteristics of the forward and reverse reactions and properties of the enzyme

Abstract

Pyruvate:ferredoxin oxidoreductase, partially purified from extracts of Clostridium acidiurici , catalyzes the oxidation and the reductive synthesis of pyruvate in addition to the exchange of CO 2 with the carboxyl group of pyruvate. The oxidation of pyruvate requires CoA, high levels of a thiol, and an electron carrier such as clostridial ferredoxin, FAD, or 2,3,5-triphenyltetrazolium chloride. DPN + cannot replace these electron acceptors in the reaction catalyzed by the purified enzyme. The reductive synthesis of pyruvate from acetyl CoA and radioactive bicarbonate requires a reduced electron carrier of low potential such as ferredoxin or methyl viologen and is stimulated by a thiol. The enzyme, whose molecular weight has been estimated to be 215,000, contains a nonheme iron chromophore, equimolar amounts of iron and sulfide, thiamine, and trace amounts of flavin. When a stoichiometric amount of enzyme is incubated with pyruvate, CoA, and thiol, in the absence of added electron acceptor, the enzyme-bound chromophore is reduced.