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The effects of nitric oxide (NO) on the nonoxidative decarboxylation of pyruvate were studied using yeast pyruvate decarboxylase (PD) as a model. PD was inhibited by NO (50% inhibition @ 0.5 mM) under anaerobic but not under aerobic conditions. Prior inhibition by NO was not reversed by aerobic conditions. Sodium nitrite (0.5 mM) was not inhibitory. Inhibition of PD by NO was markedly enhanced in the presence of -ascorbate. A preparation of pyruvate:ferredoxin oxidoreductase (PFOI from Clostridium uerfrinrrens (3624 A1 was inhibited by NO (5G% inhibition @ 0.025 mMj b; notby sodium nitrite (1.0 mM). These results suggest that the thiamin dependent decarboxylation of pyruvate may be an additional site for the antimicrobial mode of action of nitrite independent of the iron-sulfur center of PFO and supports the concept that the active principle is NO.

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