The reaction of aminoacylase with chloromethylketone analogs of amino acids.

1. Aminoacylase is irreversibly inactivated by the chloromethylketone analogs of benzyloxy-carobonyl-L-alanine, L-alanine, L-leucine, L-aspartic acid (beta), tosyl-L-phenylalanine and L-leucyl-L-alanine. The kinetics of the inactivation of the enzyme by the halo-methylketones were investigated. 2. Leucyl-and alanyl chloromethylketone inactivate the enzyme by blocking of 4 SH groups. Experiments with [U-14C]leucyl chloromethylketone confirm that maximal 4 residues are covalently bound to be protein. 3. Inactivation of the enzyme by benzyloxycarbonylalanyl and tosylphenylalanyl chloromethylketone is the result of the substitution of the epsilon-amino group of one lysine resine residue per active site and not of SH groups. However, in the presence of competitive inhibitors these halomethylketones react only with the SH groups of the enzyme, too.