Inhibition of L-Alanine Adding Enzyme by Glycine

抄録

L-Alanine adding enzymes from Bacillus subtilis and Bacillus cereus which catalyzed L-alanine incorporation into UDPMurNAc were partially purified and the properties of the enzymes were examined. The enzyme from B. subtilis was markedly stimulated by reducing agents including 2-mercaptoethanol, dithiothreitol, glutathione and cysteine. Mn²⁺ and Mg²⁺ activated L-alanine adding activity and their optimal concentrations were 2 to 5mM and 10mM, respectively. The optimum pH was 9.5 and the Km for L-alanine was 1.8×10^-4M. L-Alanine adding reaction was strongly inhibited by p-chloromercuribenzoate and N-ethyl-maleimide. Among glycine, L- and D-amino acids and glycine derivatives, glycine was the most effective inhibitor of the L-alanine adding reaction. The enzyme from B. cereus was more resistant to glycine than that from B. subtilis. Glycine was incorporated into UDPMurNAc in place of L-alanine, and the Ki for glycine was 4.2×10^-3 M with the enzyme from B. subtilis. From these data, the growth inhibition of bacteria by glycine is discussed.