摘要：Three isoforms of anionic chum salmon trypsin (ST-1, ST-2, and ST-3) were purified from the pyloric caeca of chum salmon ( Oncorhynchus keta ). The molecular weights of the three isoforms were about 24 kDa as determined by SDS-PAGE. The isoelectric points of ST-1, ST-2, and ST-3 were 5.8, 5.4, and 5.6, respectively. The apparent K m values of two isoforms (ST-1 and ST-2) for BAPA (benzoyl- L -arginine- p -nitroanilide) hydrolysis at 5, 15, 25 and 35 °C were slightly higher than that of the main isoform ST-3, depending on temperature. The turnover numbers, k cat, of ST-1 and ST-2 were about twice as high as that of ST-3. Consequently, the catalytic efficiencies ( k cat/ K m) of ST-1 and ST-2 were more efficient than ST-3. There were marked differences in both apparent K m and k cat values of three anionic chum salmon trypsins as compared to bovine cationic trypsin. K m values of all chum salmon trypsins were approximately 10 times lower than those of bovine trypsin, depending on the temperature. The k cat values of all chum salmon trypsins were about 2- to 5-fold higher than those of bovine trypsin; therefore, the catalytic efficiencies ( k cat/ K m) of chum salmon trypsin were 20- to 40-fold more efficient than those of bovine trypsin. On the other hand, k cat/ K m values of ST-1 for TAME (tosyl- L -arginine methyl ester) hydrolysis were lower than those of bovine trypsin, whereas k cat/ K m values of ST-2 and ST-3 were comparable to those of bovine trypsin, depending on the temperature.
