Activity of wheat α-amylase inhibitors towards bruchid α-amylases and structural explanation of observed specificities
Activity of wheat α-amylase inhibitors towards bruchid α-amylases and structural explanation of observed specificities
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DOI：
10.1046/j.1432-1327.2000.01199.x
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发表时间：
2000-04-01
期刊：
影响因子：
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通讯作者：
de Sá, MFG
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文献类型：
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作者：
Franco, OL;Rigden, DJ;de Sá, MFG
植物α -淀粉酶抑制剂作为作物抗病工具具有很大的潜力。然而，由于观察到酶抑制特异性的变化，甚至在密切相关的抑制剂家族中，它们的可能用途变得复杂。从小麦籽粒中分离出5个结构0.19家族的α -淀粉酶抑制剂，并对3种昆虫α -淀粉酶和猪胰腺α -淀粉酶进行了测定，揭示了几种有趣的抑制谱差异，甚至在序列相同的蛋白质之间也存在高达98%的差异。首次观察到一种重要的商业害虫——豆象（Acanthoscelides obtectus）对该酶的抑制作用。利用昆虫α -淀粉酶与结构相关抑制剂复合物的晶体结构，构建并完善了与0.19抑制剂结合的昆虫和人α -淀粉酶模型。使用这些模型成功地解释了五种抑制剂之间生化行为差异所提出的四个关键问题。残基大小和电荷、环长度以及Cys到Pro突变的构象效应是导致观察到的特异性差异的因素之一。本文报道的对0.19结构家族抑制剂特异性基础的改进结构理解，可能有助于未来合理设计具有改变抑制特性的抑制剂。
Plant alpha-amylase inhibitors show great potential as tools to engineer resistance of crop plants against pests. Their possible use is, however, complicated by observed variations in specificity of enzyme inhibition, even within closely related families of inhibitors. Five alpha-amylase inhibitors of the structural 0.19 family were isolated from wheat kernels, and assayed against three insect alpha-amylases and porcine pancreatic alpha-amylase, revealing several intriguing differences in inhibition profiles, even between proteins sharing sequence identity of up to 98%. Inhibition of the enzyme from a commercially important pest, the bean weevil Acanthoscelides obtectus, is observed for the first time. Using the crystal structure of an insect alpha-amylase in complex with a structurally related inhibitor, models were constructed and refined of insect and human alpha-amylases bound to 0.19 inhibitor. Four key questions posed by the differences in biochemical behaviour between the five inhibitors were successfully explained using these models. Residue size and charge, loop lengths, and the conformational effects of a Cys to Pro mutation, were among the factors responsible for observed differences in specificity. The improved structural understanding of the bases for the 0.19 structural family inhibitor specificity reported here may prove useful in the future for the rational design of inhibitors possessing altered inhibition characteristics.