Midgut juice plays an important role in food digestion and detoxification in insects. In order to understand the potential of midgut juice of Cnaphalocrocis medinalis (Guenée) to degrade Bt proteins, the enzymatic activity of midgut juice and its degradation of Bt proteins (Cry2A, Cry1C, Cry1Aa, and Cry1Ac) were evaluated in this study through protease inhibitor treatments. The activities of total protease in midgut juices were significantly inhibited by phenylmethylsulfonyl fluoride (PMSF), tosyl-L-lysine chloromethyl ketone (TLCK), pepstatin A and leupeptin. The enzymatic activity of chymotrypsin was significantly inhibited by PMSF, and enzymatic activity of trypsin was significantly inhibited by ethylenediaminetetraacetic acid (EDTA), PMSF, tosyl phenylalanine chloromethyl ketone (TPCK), TLCK and trans-epoxysuccinyl-L-leucylamido-(4-guanidino) butane (E-64). EDTA could significantly inhibit the degradation of Cry2A by C. medinalis. EDTA, PMSF, TPCK, and TLCK could inhibit the degradation of Cry1C and Cry1Aa. EDTA, PMSF, TPCK, TLCK, and E-64 could inhibit the degradation of Cry1Ac. Our results indicated that some protease inhibitors hindered various enzymatic activities in the larval midgut of C. medinalis, which may reduce the insect's ability to degrade Bt toxins. These findings may aid the application of protease inhibitors in the management of this insect pest in the future.

中肠汁在昆虫的食物消化和解毒中起着重要作用。为了理解中肠汁的潜在稻纵卷叶螟（螟）降解的Bt蛋白，肠汁的酶活性与Bt蛋白质（Cry2A，基因cry1C，Cry1Aa，和Cry1Ac的）的其降解在本研究中通过蛋白酶抑制剂评价治疗。苯甲基磺酰氟（PMSF）、甲苯磺酰-L-赖氨酸氯甲基酮（TLCK）、胃酶抑素A和亮抑酶肽显着抑制中肠汁中总蛋白酶的活性。PMSF显着抑制胰凝乳蛋白酶的酶活性，乙二胺四乙酸（EDTA）、PMSF、甲苯磺酰苯丙氨酸氯甲基酮（TPCK）、TLCK和反式-环氧琥珀酰-L-亮氨酰氨基-（4-胍基）丁烷（E-64）。EDTA 可以显着抑制C. medinalis对 Cry2A 的降解。EDTA、PMSF、TPCK 和 TLCK 可以抑制 Cry1C 和 Cry1Aa 的降解。EDTA、PMSF、TPCK、TLCK 和 E-64 可以抑制 Cry1Ac 的降解。我们的结果表明，一些蛋白酶抑制剂阻碍了C. medinalis幼虫中肠中的各种酶活性，这可能会降低昆虫降解 Bt 毒素的能力。这些发现可能有助于蛋白酶抑制剂在未来管理这种害虫中的应用。