PURIFICATION AND CHARACTERIZATION OF CATHEPSIN-L FROM THE WHITE MUSCLE OF CHUM SALMON, ONCORHYNCHUS-KETA

1. 1. Cathepsin L of the white muscle of chum salmon (Oncorhynchus keta) in spawning migration was purified to homogeneity by a series of chromatography on DEAE-Sephadex (1st), SP-Sephadex, CM-Sephadex, DEAE-Sephadex (2nd) and Sephadex G-100. 2. 2. The molecular weight of salmon muscle cathepsin L was estimated to be 30,000 and its isoelectric point was 5.2. 3. 3. Cathepsin L had a pH optimum of 5.6, required a thiol-reducing reagent for activation, and was inhibited by cysteine protease inhibitors. 4. 4. The Km and kcat values of Z-Phe-Arg-MCA were determined to be 1.68 μM and 15.8 s-1, respectively. This enzyme hydrolyzed proteins such as insulin B chain, hemoglobin, serum albumin and azocasein easily. 5. 5. The bond specificity to oxidized insulin B chain inferred that the enzyme had a preference for hydrophobic amino acid in P2 and P3 residues. © 1990.