小枯草桿菌BL11木聚醣酶XylX碳水化合物模組結構研究結合

Abstract

一分離自黑液前漂漿的Paenibacillus campinasensis BL11菌株可分泌出許多針對不同多醣類的水解型酵素，其中有一β-1,4-鍵結內切型木聚醣酶（命名為XylX）在不同pH值展現出優異的酵素活性作用，同時擁有良好的溫度耐受性。因此，此酵素被認為是利用於木聚醣降解相關之生物工程產業上為一良好候選者。酵素XylX具有一非催化性片段，其為碳水化合物結合模組（carbohydrate binding module, CBM），此蛋白模組是常見於水解型酵素中的一輔助型片段，而此模組通常依附於催化區段，並負責調控與不可溶的碳水化合物的專一性吸附作用，藉以提升整體酵素的水解效果。於此論文中，我們利用核磁共振針對XylX當中的第36號家族的碳水化合物結合模組之蛋白質進行研究，完成了核磁共振光譜中主鏈與側鏈於之循序判定，除此並結合其他分子生物檢測工具藉以了解其基本結構與功能之關聯性，其中包括對其基質作用之專一性及親和性、蛋白質二級與三級結構的預測以及確認木聚醣和鈣離子於此蛋白質上所結合的區域；相信此資訊將有利於未來對於碳水化合物結合模組與碳水化合物之動態分析以及於醣甘鍵結水解酶上的生物工程之應用。

Paenibacillus campinasensis BL11 was isolated from black liquor and secretes multiple hydrolytic enzymes against various polysaccharides. One of endo-β-1, 4-xylanase (denote as XylX) demonstrates a high enzymatic activity in a wide range of pH and thermal endurance, that has been considered as an excellent candidate in xylan-degrading related biotechnological processing. XylX contains one non-catalytic domain, i.e. carbohydrate binding module (CBM); which is most frequently appeared ancillary domain in hydrolases. These kinds of modules usually appended to catalytic domain and mediate the specific interaction with insoluble carbohydrate to promote hydrolysis efficiency of entire enzyme. In this work, we conducted a NMR study of CBM segment of family 36 (PcCBM36) derived from XylX. And the backbone and side-chain sequential resonance assignments were completed. In addition, in combination with other biophysical tools, we have studied the structural and functional properties of PcCBM36, including secondary and tertiary structural prediction and its binding behavior against endo-β-1, 4-xylan linkage and calcium ion. As believed, this study will facilitate molecular dynamics analysis of interaction between CBMs and carbohydrate, whereas the engineering for glycoside hydrolases (GHs).