Abstract
Cathepsin B [EC 3. 4. 22. 1] from the liver of squid, Dorytheuthis bleekri, was purified by the following steps: homogenization, ammonium sulfate fractionation, CM-cellulose column chromatography and rechromatography, Sephadex G-75 column chromatography and isoelectric focusing. The purified enzyme appears to be homogeneous by polyacrylamide gel electrophoresis at both pH 4.3 and pH 9.5 and has an isoelectric point of 6.8. The molecular weight of the enzyme was determined to be 13, 600 by Sephadex G-75 column chromatography. The optimum pH for hydrolysis of α-N-benzoyl-L-argininamide (BAA), α-N-benzoyl-DL-arginine-2-naphthylamide (BANA) was 4.5, and it was 4.2_??_4.7 for N, N'-dimethyl hemoglobin. The value of Km for the hydrolysis of BANA was estimated to be 1.25mM.
