Structure, Catalysis, and Inhibition of OfChi-h, the Lepidoptera-exclusive Insect Chitinase

文献类型： 外文期刊

第一作者： Chen, Lei

作者： Chen, Lei;Zhou, Yong;Jiang, Xi;Duan, Yanwei;Yang, Qing;Liu, Tian;Chen, Lei;Zhou, Yong;Jiang, Xi;Duan, Yanwei;Yang, Qing;Yang, Qing

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期刊名称：JOURNAL OF BIOLOGICAL CHEMISTRY （ 影响因子：5.157； 五年影响因子：5.041 ）

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收录情况： SCI

摘要： Chitinase-h (Chi-h) is of special interest among insect chitinases due to its exclusive distribution in lepidopteran insects and high sequence identity with bacterial and baculovirus homologs. Here OfChi-h, a Chi-h from Ostrinia furnacalis, was investigated. Crystal structures of both OfChi-h and its complex with chitoheptaose ((GlcN) 7) reveal that OfChi-h possesses a long and asymmetric substrate binding cleft, which is a typical characteristics of a processive exo-chitinase. The structural comparison between OfChi-h and its bacterial homolog SmChiA uncovered two phenylalanine-to-tryptophan site variants in OfChi-h at subsites +2 and possibly -7. The F232W/F396W double mutant endowedSmChiA with higher hydrolytic activities toward insoluble substrates, such as insect cuticle, alpha-chitin, and chitin nanowhisker. An enzymatic assay demonstrated that OfChi-h outperformed OfChtI, an insect endochitinase, toward the insoluble substrates, but showed lower activity toward the soluble substrate ethylene glycol chitin. Furthermore, OfChi-h was found to be inhibited by N, N',N"-trimethylglucosamine- N, N',N",N"'-tetraacetylchitotetraose (TMG(GlcNAc)(4)), a substrate analog which can be degraded into TMG-(GlcNAc)(1-2). Injection of TMG-(GlcNAc)(4) into 5th-instar O. furnacalis larvae led to severe defects in pupation. This work provides insights into a molting-indispensable insect chitinase that is phylogenetically closer to bacterial chitinases than insect chitinases.

分类号： Q5

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