從浸水條件環境下生長的稻米芽鞘，可經由陽離子交換管柱及膠體管柱層析的方式分離出一種分子量大約在18 kDa的胰蛋白"酉每"抑制劑。我們已經進一步探討此抑制劑對於胰蛋白"酉每"及胰凝乳蛋白"酉每"的抑制行為。於研究中發現，此抑制劑對於胰凝乳蛋白"酉每"水解受質N-苯甲醯基-精胺酸-對硝基苯胺（L-BAPNA）的抑制行為並非一個典型的競爭型抑制反應；但是其對於胰蛋白"酉每"水解同一受質的抑制機制與從大豆中萃取出的胰蛋白"酉每"抑制劑相同，都屬於競爭型的抑制反應。
從稻米芽鞘中取得的抑制劑與胰蛋白"酉每"結合之複合物（EI），其解離常數為4.0 ×10-7 M，而從大豆中萃取出的抑制劑與同一酵素結合之複合物（EI），其解離常數為7.4 X 10-7 M。當稻米抑制劑與胰蛋白"酉每"之濃度比為0.3時，可抑制百分之五十的胰蛋白"酉每"對受質L-BAPNA之水解活性，而黃豆抑制劑則需約0.5的比率才能抑制百分之五十的胰蛋白"酉每"對同一受質之水解活性。此研究結果顯示對胰蛋白"酉每"而言，稻米芽鞘所萃取出的抑制劑的抑制能力比大豆所萃取出的抑制劑為佳。因此，對此抑制劑更進一步的研究，在醫藥及食品上之應用，是一個重要且值得去探討之課題。

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.

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