耐热阿拉伯糖苷酶三维结构模拟和底物对接分析

Modeling of the 3D Structure of Thermostable Arabinosidase and Insight into the Binding Mode of Substrate by Molecular Docking

阿拉伯糖苷酶能催化L-阿拉伯糖和木糖间糖苷键的水解,在半纤维素降解及阿拉伯糖制备过程中有重要作用。源自乙醇热厌氧杆菌Thermoanaerobacter ethanolicus的阿拉伯糖苷酶具有阿拉伯糖苷酶和木糖苷酶的双重活性,且具有高度的热稳定性。为深入研究该酶的催化机理,预测了该酶的空间结构和活性中心关键残基,以便指导进一步的实验研究;使用同源模建的方法,以Thermotoga neapolitanaβ-糖苷酶3b的结构为模版,模建了T.ethanolicus阿拉伯糖苷酶的结构,并使用分子对接的方法,将底物对硝基苯基-L-阿拉伯糖苷(pNPAP)和对硝基苯基-D-木糖苷(pNPX)对接到酶的活性中心;预测的底物-酶复合物结构表明酶活性中心Asn90、Arg164、Lys201、Asp281等残基在底物结合和水解过程中可能发挥有重要的作用。

Arabinosidase can catalyze the hydrolysis of the glycoside bond between L-Arabinose and xylose, and release arabinose from hemicellulose, therefore it plays important role in the degradation of hemicellulose and the preparation of arabinose. The arabino- sidase from the anaerobic thermophile Thermoanaerobacter ethanolicus poses the double functional activity of xylosidase and arabinnsidase,and is a thermostable enzyme. In order to further study the catalytic mechanism, the 3D structure of the arabinosidase was predicted. It also figured out the important residues in the predicted structure. The homology modeling method was used to predict its structure, using the structure of the ^-glucosidase from Thermotoga neapolitana as template. The substrate of p-nitrophenyl ct-L-arabi- nopyranoside （pNPAP） and p-nitrophenyl ~,-D-xylopyranoside （pNPX） were docked into the active site of the predicted structure of the arabinosidase, respectively. The results showed that the residue of Asn90, Arg164, Lys201 and Asp281 on the active site may play important role in substrate binding and hydrolyzing process.