Intermediates in the biosynthesis of bacterial penicillinase

would seem to be a specially favourable case for demonstrating inhibition by toxopyrimidine phos- phate, since the coenzyme spontaneously dissociated from the apoenzyme as decarboxylation proceeded (Fig. But, even here, only slight inhibition was observed, whereas in the valine de- carboxylation (when the coenzyme is more firmly bound) no inhibition was detected under the ex- perirnental conditions. Nevertheless, there are probably cases where toxopyrimidine or its phos- phate can severely inhibit unresolved enzymes: otherwise, the toxicity to animals at relatively low toxopyrimidine:pyridoxal ratios is difficult to explain. SUMMARY 1. Toxopyrimidine phosphate failed to inhibit unresolved bacterial arginine and glutamic de- carboxylases, tryptophanase and glutamate-alanine transaminase.