一种苦荞麦种子蛋白酶抑制剂的纯化、特性及其抗虫活性

蛋白酶抑制剂广泛存在于生物体内, 是自然界含量最为丰富且具有一定防御作用的蛋白种类之一. 本文采用离子交换层析和凝胶层析等方法，从苦荞麦种子中分离出一种胰蛋白酶抑制剂（TBTI-Ⅱ）. SDS-PAGE分析表明,TBTI Ⅱ的分子量约9.0 kD，由80个氨基酸残基组成，分子中含有较多的 Glu, Asp 和Arg. TBTI-Ⅱ具有较高热稳定性.当在100℃加热处理10 min后,仍保留有67.6%的抑制剂活性. 动力学测定显示,来自苦荞麦中的TBTI-Ⅱ对胰蛋白酶的抑制作用常数(Ki)为1.01×10－4 mol/L. 另外,将含有不同活力单位的苦荞麦蛋白酶抑制剂掺入到棉铃虫的饲料中进行饲养试验显示，TBTI-Ⅱ具有明显的抑制棉铃虫生长的作用. 这些结果表明，来自苦荞麦种子中的小分子蛋白酶抑制剂可能是一种潜在的抗虫因子.

Purification and Characterization of a Protease Inhibitor from Fagopyrum tartaricum Gaertn Seeds and Its Effectiveness Against Insects

Protease inhibitors, which are widely distributed in all types of life forms, are generally considered to be one of the most abundant proteins and a defense mechanism. A protease inhibitor from tartary buckwheat seeds (TBTI-Ⅱ ), with specific trypsin-inhibitory activity, was obtained by Resource Q anion-exchange chromatography and Superdex G 75 gel filtration. SDS-PAGE analysis indicated that the approximate molecular weight was 9.0 kD. Amino-acid analysis showed that the TBTI- Ⅱ was composed of 80 amino-acid residues with a high content of glutamate, aspartate and arginine. The inhibitor had high thermostability and retained 67.6% of its activity after heating at 100℃ for 10 min. The inhibition constant Ki was determined to be 1.01× 10-4 mol/L. It was demonstrated that the inhibitor was able to have an effect on the growth of cotton bollworm larva, after being fed with the artificial diets mixed with the target inhibitor. The present study indicates that the trypsin inhibitor from tartary buckwheat seeds could be a new potential anti-insect factor.