木聚糖酶与XIP型木聚糖酶抑制蛋白相互作用分子机制的研究进展

Interaction between xylanase and XIP-type xylanase inhibitor protein: a review

Xylanase inhibitor protein(XIP)型木聚糖酶抑制蛋白对大部分GH10、GH11家族的真菌木聚糖酶具有抑制作用,但是却不能抑制细菌来源和植物自身所产生的木聚糖酶。XIP型木聚糖酶抑制蛋白对木聚糖酶的抑制作用主要是通过模拟底物接触酶的活性位点,迅速阻塞底物进入活性位点区域的通道。然而,在对XIP型木聚糖酶抑制蛋白具有抗性的GH10和GH11木聚糖酶晶体结构中,连接二级结构的Loop构象严重阻碍了XIP型木聚糖酶抑制蛋白的抑制功能。与对XIP型木聚糖酶抑制蛋白敏感的木聚糖酶相比,氨基酸残基的插入突变导致抗性木聚糖酶的Loop具有明显的凸出构象;而在GH11家族抗性木聚糖酶中,"拇指"结构中部分氨基酸的替换致使XIP型木聚糖酶抑制蛋白与"拇指"结构无法形成稳固的氢键和疏水建,从而削弱XIP的抑制作用。

XIP-type xylanase inhibitor proteins have inhibitory effects on most fungal xylanases of the GH10 and GH11 families,but they cannot inhibit xylanase produced by plants and bacteria.The inhibitory effect of XIP-type xylanase inhibitor protein on xylanase is mainly through simulating substrate contacting the active site of the enzyme,and quickly blocking the channel of the substrate into the active site region.However,in the crystal structures of GH10 and GH11 xylanase that are resistant to XIP-type xylanase inhibitor proteins,the loop conformations linking secondary structures obviously hinder the inhibition of XIP-type xylanase inhibitor proteins.Compared with XIP-sensitive xylanase,the insertion mutation of amino acid residues results in a prominent conformation of the loop of resistant xylanase.In XIP-resistant GH11 xylanase,the substitution of some amino acids in the thumb structure prevents the XIP-type xylanase inhibitor protein from forming a stable hydrogen bond and hydrophobic structure with the thumb structure,thereby weakening the inhibitory effect of XIP.