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DEGRADATION OF PYRUVATE BY MICROCOCCUS LACTILYTICUS III.

Properties and Cofactor Requirements of the Carbon Dioxide-Exchange Reaction

^a Department of Microbiology, University of Washington, Seattle, Washington

ABSTRACT

WHITELEY, H. R. (University of Washington, Seattle) AND N. G. MCCORMICK. Degradation of pyruvate by Micrococcus lactilyticus. III. Properties and cofactor requirements of the carbon dioxide-exchange reaction. J. Bacteriol. 85:382–393. 1963.—At an acid pH, extracts of Micrococcus lactilyticus (Veillonella alcalescens) catalyze the oxidative decarboxylation of pyruvate to carbon dioxide, hydrogen, and acetyl phosphate, and the rapid exchange of carbon dioxide into the carboxyl group of pyruvate. These reactions take place only under anaerobic conditions and require phosphate (or arsenate), a reducing agent, diphosphothiamine, coenzyme A, an electron acceptor (ferredoxin, flavins, dyes, or certain inorganic anions), and a divalent cation (Co⁺⁺> Mn⁺⁺ > Mg⁺⁺ > Fe⁺⁺). High concentrations of coenzyme A and electron acceptors stimulate pyruvate breakdown but inhibit CO₂ exchange. Exchange is also inhibited by p-chloromercuribenzoate but not by arsenite. Extracts rapidly lose the ability to mediate the exchange reaction after passage through diethylaminoethyl- or triethylaminoethyl-cellulose or Dowex-1; this loss in activity may be prevented by adding a reducing agent and the above cofactors. The exchange of CO₂ and formate by M. lactilyticus is compared.

¹ Present address: Department of Microbiology, University of Virginia, Charlottesville.

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