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标题：Kinetic Properties of Three Isoforms of Trypsin Isolated from the Pyloric Caeca of Chum Salmon (Oncorhynchus keta)
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作者：Eiko Toyota ; Daisuke Iyaguchi ; Haruo Sekizaki 等
期刊名称：Biological and Pharmaceutical Bulletin
印刷版ISSN：0918-6158
电子版ISSN：1347-5215
出版年度：2007
卷号：30
期号：9
页码：1648-1652
DOI：10.1248/bpb.30.1648
出版社：The Pharmaceutical Society of Japan
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.
关键词：trypsin;isoform;chum salmon;Oncorhynchus keta;characterization;catalytic efficiency