稻米芽鞘胰蛋白"酉每"抑制劑之純化與特性

A rice trypsin inhibitor with molecular of around 18 KDa has been obtained through cationic and gel filtration columns from coleoptiles grown under submerge condition. This trypsin inhibitor was further characterized toward proteases of chymotrpsin and trypsin. It was found that the inhibition mode when competing with substrate L-N-α-benzoyl-arginine-para- nitroanilide (L-BAPNA) toward chymotrypsin was not a typical competitive mode. However, the inhibition mode when competing with L-BAPAN toward trypsin was found a typical competitive mode as that of soybean trypsin inhibitor. The EI complex dissociation constant, Kd, for rice trypsin inhibitor, toward trypsin was 4.0 x 10-7M, while it was 7.4 x 10-7M for soybean trypsin inhibitor. When the molar ratio of Rice trypsin inhibitor to trypsin was about 0.3, 50% of trypsin activity had been inhibited; while it was about 0.5 for soybean trypsin inhibitor. This study shows that rice trypsin inhibitor has better inhibition activity than soybean trypsin inhibitor does toward trypsin. Thus, it would be interesting and important to investigate further in the application of this inhibitor in medicinal and food chemistry.