Inhibitory modes of Kunitz and Bowman-Birk soybean trypsin inhibitors to tryptic and chymotryptic proteinases of tiger puffer and yellowtail

An inhibitory effect of Kunitz and Bowman-Birk soybean trypsin inhibitors ( K- and BB-SBTl) was investigated on tryptic and chymotryptic proteinases of a brood of tiger puffer Takifugu rubripes and yellowtail Seriola quinquera diata. These assist to comprehend the differences in dietary soybean meal ( SBM) utility by fish species and to develop low cost SBM diets with low con tents of fish meal. The K-SBTl strongly inhibited tryptic proteinase and we akly inhibited chymotryptic proteinase from the hepatopancreas and intestin e including pyloric ceca of the fishes. The BB-SBTI strongly inhibited both proteinases of the fishes. The K-SBTl inhibition for tryptic protease and the BB-SBTI inhibition for tryptic and chymotryptic proteases were relative ly constant in tiger puffer with growth of 12-199g bodyweight. In yellowtai l with growth of 7-672 g bodyweight, the K-SBTl inhibition for tryptic prot ease and the BB-SBTl inhibition for chymotryptic protease were also relativ ely constant. The BB-SBTl inhibition for yellowtail tryptic protease typica lly fell in the stage from 7g to 57g bodyweight, and then decreased slightl y or was maintained constantly. These results indicate that there are diffe rent inhibitory modes of K- and BB-SBTl and there is inter- and intraspecif ic diversity of tryptic protease conformation between the two species.