中文摘要：

决明胰蛋白酶抑制剂1（Co TI1）属于Kunitz胰蛋白酶抑制剂家族成员,通过序列比对预测Arg86、Leu84和Thr88等3个氨基酸残基可能是Co TI1发挥抑制作用的关键残基。通过定点突变的方法将Arg86、Leu84与Thr88残基分别突变为Asp残基,并考察各突变体对胰蛋白酶及棉铃虫等鳞翅目害虫消化酶的抑制作用。与Co TI1相比,Co TI1~（R86D）、CoTI1~（T88D）与CoTI1~（L84D）突变体对胰蛋白酶的抑制活性分别下降了93%、64%与59%;对棉铃虫、甜菜夜蛾、斜纹夜蛾等3种鳞翅目害虫消化酶的平均抑制活性分别下降了88.7%、57%与60.7%。以上结果表明Arg86、Leu84与Thr88是Co TI1发挥抑制作用的关键残基,这为Co TI1的抑制分子机制及抗虫研究提供了重要的理论依据。

英文摘要：

A trypsin inhibitor（ CoTI1） from Cassia obtusifolia was attributed to the Kunitz-type trypsin inhibitor family. According to the sequence alignment,Arg86,Leu84 and Thr88 might be the key residues of CoTI1. In order to confirm the speculation,the three above residues were replaced as Asp by site-directed mutagenesis,respectively,and analysis the inhibitory activity of the mutants and Co T1 to trypsin and insects＇ digestive enzyme. Compared with CoT1,the inhibitory activity of the mutant CoTI1~（R86） Dto trypsin decreased most obviously,and the inhibitory effect of the original 93% was lost. CoTI1~（L84D） lost 59% of the inhibitory effect;while the inhibitory activity of CoTI1~（T88D） decreased by 64%. The average inhibitory activity decreased 88. 7%,57% and 60. 7% to digestive enzymes of Helicoverpa armigera, Beet armyworm and Spodoptera litura,respectively. The result shows that Arg86,Leu84 and Thr88 are the key residues of Co T1,and it was useful for the molecular mechanism and anti-insects study of CoTI1.