不同家蚕品系的胰蛋白酶抑制剂种类与活性的多态性分析

Polymorphism Analysis on the Type and Activity of Trypsin Inhibitors from Different Bombyx mori Strains

胰蛋白酶抑制剂（trypsin inhibitor,TI）广泛存在于昆虫体内,可抑制胰蛋白酶的水解活性。采用非变性聚丙烯酰胺凝胶电泳和蛋白酶活性染色的方法,研究不同家蚕品系的丝腺、同一品系家蚕的不同组织器官及不同发育时期丝腺中胰蛋白酶抑制剂种类和活性的多态性,以丰富家蚕丝蛋白的合成、分泌及保护机制研究的基础信息。在22个家蚕品系上蔟第2天的蚕体丝腺中,共检测到6种胰蛋白酶抑制剂,分别命名为TI-Ⅰ~TI-Ⅵ,其中大部分家蚕品系都有TI-Ⅵ,有TI-Ⅳ的品系也较多,而有TI-Ⅱ的品系最少,家蚕不同品系间TI的种类分布不一致;在幼虫5龄期,TI活性随着丝腺的发育逐渐增强;在家蚕品系大造上蔟第1天蚕体的7个组织器官中,只在血液、精巢和丝腺中检测到TI,其中血液和丝腺中各检测到2种TI,精巢中检测到1种TI,而且同一家蚕品系含有TI的组织器官中的TI种类也不一致。对茧丝中3种TI（TI-Ⅲ、TI-Ⅳ和TI-Ⅵ）的理化性质进行检测,发现不同种类TI对温度及p H的适应范围不同,其中TI-Ⅵ的适应范围较广。研究结果显示：不同家蚕品系丝腺中含有的TI种类以及6种TI活性的强弱表现出多态性;同一家蚕品系不同组织器官中的TI种类也具有多态性;温度和p H对不同TI的活性影响程度不同。

Trypsin inhibitor（ TI）,a protein which can inhibit the activity of trypsin,is widespread in insects. In this study,native polyacrylamide gel electrophoresis followed by active staining was employed to study the polymorphism of TI type and its activity in silk gland of different silkworm（ Bombyx mori） strains,different tissues of the same silkworm strain,and different developmental stages of silk gland to enrich the basic information of silk protein synthesis,secretion and protection mechanisms. A total of 6 types of TI were detected in silk gland of 22 silkworm strains at day 2 after mounting and designated as TI-Ⅰ,TI-Ⅱ,TI-Ⅲ,TI-Ⅳ,TI-Ⅴ,TI-Ⅵrespectively,in which TI-Ⅵ and TI-Ⅳexisted in most silkworm stains, while TI-Ⅱ was detected in a very few strains. And the inconsistent distribution of TI in different silkworm strains implied its polymorphism. In the fifth instar,the activity of TI increased gradually with the development of silk gland. In seven tissues of silkworm variety Dazao at the first day of wandering stage,TI was detected in blood,silk gland and testis. Two types of TI were detected in blood and silk gland,while only one type of TI was detected in testis. Besides,the type of TI was different in the tissues containing TI of the same silkworm strain. Physicochemical property test of 3 types of TI in cocoon silk indicated that the adaption to temperature and p H was different for different types of TI,and those with TI-Ⅵ can endure a wider change of temperature and p H. These results showed that the type and activity of TI in silk gland had polymorphism among different silkworm strains. Furthermore,the type of TI had polymorphism among different tissues of the same silkworm stain. And the adaption to temperature and p H was also different for different types of TI.