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L-cysteine oxidase activity in the membrane of Neisseria meningitidis.

ABSTRACT

Among the L-amino acids, only L-cysteine was oxidized by isolated washed membranes of group B Neisseria meningitidis SD1C. The cysteine oxidase in the membrane obeyed Michaelis-Menten kinetics and was heat labile. The pH optimum for the maximum velocity of the reaction was 9.8. Specific activity of the enzyme increased as cell growth progressed through the exponential phase toward the stationary phase of growth. The enzyme activity was markedly sensitive to inhibition by metal chelators, but was resistant to inhibitors of terminal oxidases with the exception of cyanide. All known cytochromes in the membrane, except b563, were reduced with L-cysteine. The additive nature of L-cysteine oxidase and succinate oxidase activities suggests that an unidentified oxidase is involved in the oxidation of cysteine.