title: Evidence for an active-center cysteine in the SH-proteinase alpha-clostripain through use of N-tosyl-L-lysine chloromethyl ketone.
abstract: The rapid reaction of alpha-clostripain with tosyl-L-lysine chloromethyl ketone results in a complete loss of activity and in the disappearance of one titratable SH group whereas the number of histidine residues is not affected. Tosyl-L-phenylalanine chloromethyl ketone and phenylmethylsulfonyl fluoride have no effect on the catalytic activity. From the molar ratio and under the assumption of 1:1 molar interaction, the fully active enzyme has a specific activity of 650-700 units/mg [twice the value proposed by Porter et al. (J. Biol. Chem. 246 (1971) 7675-7682)]. Partial oxidation makes it experimentally impossible to attain this maximal value.
mesh_terms: D000477:Alkylating Agents / Q000494:pharmacology; D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology*; D001665:Binding Sites; D003013:Clostridium / Q000201:enzymology; D003545:Cysteine / Q000037:antagonists & inhibitors; D003546:Cysteine Endopeptidases; D006639:Histidine; D006863:Hydrogen-Ion Concentration; D011480:Protease Inhibitors; D014107:Tosyllysine Chloromethyl Ketone / Q000494:pharmacology*
chemical_list: D000477:Alkylating Agents; D000590:Amino Acid Chloromethyl Ketones; D011480:Protease Inhibitors; D014107:Tosyllysine Chloromethyl Ketone; D006639:Histidine; D003546:Cysteine Endopeptidases; C019913:clostripain; D003545:Cysteine