Modification of a zinc proteinase from Bacillus mesentericus strain 76 by diethylpyrocarbonate

Diethylpyrocarbonate (DEPC) inactivated the neutral zinc proteinase from Bacillus mesentericus strain 76/Bacillus subtilis (MCP 76) by ethoxycarbonylation completely. Exposure of the enzyme to DEPC together with the competitive inhibitor Z-L-phenylalanine prevented the loss of activity toward both peptide and protein substrates. Treatment with hydroxylamine restored the catalytic properties of the modified MCP 76 to that of the native enzyme. After chymotryptic digestion of ethoxycarbonylated MCP 76 in the presence and absence of Z-L-phenylalanine a single histidyl residue essential for the enzyme activity was isolated and identified as histidine 231.