水稻巯基蛋白酶抑制剂的分子修饰与其对稻瘟病菌的抑制作用

The Molecular Modification of Cysteine Proteinase Inhibitor from Rice Seed and its Inhibition on Rice Blast

水稻巯基蛋白酶抑制剂（ＣＰＩ）经用二硫苏糖醇，对氯汞苯甲酸和碘乙酸修饰后，对木瓜蛋白酶的抑制活性并无改变；用Ｎ－乙基顺丁烯二酰亚胺与ＣＰＩ反应，可以测出ＣＰＩ分子内有１９个巯基被修饰，被修饰后，抑制活性仍无改变，表明水稻ＣＰＩ的抑制活性不需要巯基参与；应用Ｎ－溴代丁二酰亚胺与ＣＰＩ反应，可测出ＣＰＩ分子内有２个Ｔｒｐ被修饰，修饰后，抑制活性全部丧失，表明Ｔｒｐ是保持抑制活性所必需的基团。水稻巯基蛋白酶抑制剂和丝氨酸蛋白酶抑制剂对稻瘟病菌丝体的生长均有抑制作用，但后者的抑制作用比前者更强，若将两种抑制剂混合使用，则对稻瘟病菌丝体的抑制作用非常强烈；当抑制剂加入量达７２μｇ时，即可产生明显的抑制作用。

The cysteine proteinase inhibitor(CPI) from rice seed could retain all its activity of inhibition after modification of sulfhydryl group with dithiothreitol, p-chloromercuric benzoic and iodoacetic acid. Ninteen sulfhydryl groups in the CPI were modified by N-ethylmaleimide, but the inhibition activity of CPI did not change. These results showed that sulfhydryl groups did not influence the inhibition of CPI. Tryptophan (Trp) in the CPI was modified with N-bromosuccinimide,the result showed that there were two Trp in the CPI, and the modified CPI lost the activity of inhibition completely, so Trp is important and essential for keeping the inhibition activity of the CPI. Both the CPI and serine proteinase inhibitor(SPI) from rice seed could inhibit the growth of rice blast hyphostoma, and the inhibition of SPI was stronger than that of CPI. The mixture of SPI and CPI was able to inhibit the growth of rice blast hyphostoma at the dosage of 72 μg.