alpha-Clostripain. Chemical characterization, activity, and thiol content of the highly active form of clostripain

A highly active form of clostripain, composed of two polypeptide chains (Mr = 43,000 and 12,500), was isolated by hydrophobic chromatography from the culture medium of Clostridium histolyticum. It differs in amino acid composition, namely in the value for cyst(e)ine, from that previously reported. The analyses of the separated chains are given. Activity is related to the number of free cysteine residues and full activity is obtained only after complete reduction of the disulfide bonds. Specific modifications by sulfhydryl reagents and tosyl lysine chloromethyl ketone of one thiol group, the one implicated in the activity, are reported. High specificity of alpha-clostripain is restricted to arginyl peptide bonds as tested on parvalbumin.