A general framework of cysteine-proteinase mechanism deduced from studies on enzymes with structurally different analogous catalytic-site residues Asp-158 and −161 (papain and actinidin), Gly-196 (cathepsin B) and Asn-165 (cathepsin H). Kinetic studies up to pH 8 of the hydrolysis of N-α-benzyloxycarbonyl-l-arginyl-l-arginine 2-naphthylamide catalysed by cathepsin B and of l-arginine 2-naphthylamide catalysed by cathepsin H.