Figure 1. Metabolism of pyruvate to acetate in Clostridia. The "phosphoroclastic" conversion of pyruvate to acetate is mediated by several iron-containing proteins. Pyruvate-ferridoxin oxidoreductase oxidizes pyruvate, using ferridoxin (Fd) as the electron acceptor. Reduced ferridoxin is then re-oxidized by a third iron-containing protein, hydrogenase. Protons serve as the electron acceptor, and hydrogen gas is formed. Phospho-transacetylase and acetate kinase catalyze the final two steps, with acetate and one mole of ATP formed as end products. Importantly, both pyruvate-ferridoxin oxidoreductase and ferridoxin are able to form complexes with nitric oxide. This would effectively block this pathway, depriving cells of ATP, as well as increasing the concentration of pyruvate to potentially toxic levels. Adapted from White, 2000.
Cammack, R., C.L. Joannou, X.-Y Cui, C.T. Martinez, S.R. Maraj, and M.N. Hughes. 1999. Nitrtie and nitrosyl compounds in food preservation. Biochim. Biophys.Acta. 1411:475-488.
Grever, A.B.G., and A. Ruiter. 2001. Prevention of Clostridium outgrowth in heated and hermetically sealed meat by nitrite—a review. Eur. Food Res.Technol. 213:165-169.
White, D. 2000. The physiology and biochemistry of prokaryotes, second edition. Oxford University Press, Inc., New York.
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