Purification and some properties of cathepsin B from rabbit skeletal muscle

Cathepsin B was purified from rabbit skeletal muscle by ammonium sulfate fractionation and successive chromatographies on Sephadex G-75, phosphocellulose, peptide-conjugated Sepharose, DEAE-Toyopearl and Sephadex G-100. The purified enzyme gave a single protein band on SDS/polyacrylamide gel electrophoresis. The enzyme did not abolish the Ca sensitivity of the ATPase activity of myofibrils. The molecular mass of the enzyme was found to be 27 kDa on gel filtration and SDS/polyacrylamide gel electrophoresis. The optimum pH for the hydrolysis of N alpha-benzoyl-DL-arginine-beta-naphthylamide was 6.5. The enzyme was stable in the range of pH 4.5-5.5. Tetrathionate reacted with thiol groups of the enzyme reversibly so that it stabilized the enzyme. The enzyme was strongly inhibited by iodoacetate, HgCl2, antipain, leupeptin, N alpha-p-tosyl-L-lysine chloromethane and L-tosylphenylalanylchloromethane, but not by pepstatin or trypsin inhibitor.