The antifungal activity of insect chitinase has rarely been studied. Here, we show that chitinase ChtIV, which is specifically expressed in the midgut of Asian corn borer (Ostrinia furnacalis), has antifungal activity toward phytopathogenic fungi. ChtIV exhibited high stability and mycelial hydrolytic activity in the extreme midgut environment, which has a pH of 10 and is rich in proteases. Hyper-N-glycosylation and reduced electrostatic interactions ensure the stability of ChtIV in the midgut. The structural characteristics of ChtIV are similar to two plant antifungal chitinases but distinct from an insect chitinase for cuticular chitin degradation in both the substrate-binding cleft and auxiliary binding motif. Since the phytopathogenic fungi are those that frequently invade corn, ChtIV may play a role in insect immune system and become a potential pesticide target. The crystal structures of ChtIV and its complexes with penta-N-acetylchitopentaose (a substrate) and allosamidin (an inhibitor) were obtained, which may facilitate rational design of ChtIV inhibitors as agrichemicals.

中文翻译：

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具有抗真菌活性的昆虫肠道特异性几丁质酶的结构和生化见解。

昆虫几丁质酶的抗真菌活性很少被研究。在这里，我们显示几丁质酶ChtIV，特别是在亚洲玉米bore（Ostrinia furnacalis）的中肠中表达，对植物致病真菌具有抗真菌活性。ChtIV在极端中肠环境中表现出高稳定性和菌丝体水解活性，该环境的pH为10，并且富含蛋白酶。高N-糖基化和减少的静电相互作用确保ChtIV在中肠的稳定性。ChtIV的结构特征类似于两种植物抗真菌几丁质酶，但与昆虫几丁质酶在基质结合裂口和辅助结合基序中的表皮甲壳质降解不同。由于植物致病真菌是经常入侵玉米的真菌，ChtIV可能在昆虫的免疫系统中起作用，并成为潜在的杀虫剂目标。获得了ChtIV的晶体结构及其与五-N-乙酰基甲壳五糖（一种底物）和异黄素（一种抑制剂）的配合物，这可能有助于合理设计ChtIV抑制剂作为农用化学品。