| Title |
The Role of Carbohydrate-Binding Module (CBM) Repeat of a Multimodular Xylanase (XynX) from Clostridium thermocellum in Cellulose and Xylan Binding |
| Author |
Thangaswamy Selvaraj1, Sung Kyum Kim1, Yong Ho Kim1, Yu Seok Jeong1, Yu-Jeong Kim1, Nguyen Dinh Phuong1, Kyung Hwa Jung2, Jungho Kim1, Han Dae Yun3, and Hoon Kim1* |
| Address |
1Department of Agricultural Chemistry, Sunchon National University, Suncheon 540-742, Republic of Korea, 2Amicogen, Inc., 694-4 Sangchon, Jinsung, Jinju 660-852, Republic of Korea, 3Division of Applied Life Science, and Research Institute of Life Science, Gyeongsang National University, Chinju 660-701, Republic of Korea |
| Bibliography |
Journal of Microbiology, 48(6),856-861, 2010,
|
| DOI |
|
| Key Words |
Clostridium thermocellum XynX, truncated xylanases, gel-elution, carbohydrate-binding module, cellulose and xylan binding |
| Abstract |
A non-cellulosomal xylanase from Clostridium thermocellum, XynX, consists of a family-22 carbohydratebinding module (CBM22), a family-10 glycoside hydrolase (GH10) catalytic module, two family-9 carbohydrate-binding modules (CBM9-I and CBM9-II), and an S-layer homology (SLH) module. E. coli BL21(DE3) (pKM29), a transformant carrying xynX', produced several truncated forms of the enzyme.
Among them, three major active species were purified by SDS-PAGE, activity staining, gel-slicing, and diffusion from the gel. The truncated xylanases were different from each other only in their C-terminal regions. In addition to the CBM22 and GH10 catalytic modules, XynX1 had the CBM9-I and most of the CBM9-II, XynX2 had the CBM9-I and about 40% of the CBM9-II, and XynX3 had about 75% of the CBM9-I. The truncated xylanases showed higher binding capacities toward Avicel than those toward insoluble xylan. XynX1 showed a higher affinity toward Avicel (70.5%) than XynX2 (46.0%) and XynX3 (42.1%); however, there were no significant differences in the affinities toward insoluble xylan. It is suggested that the CBM9 repeat, especially CBM9-II, of XynX plays a role in xylan degradation in nature by strengthening cellulose binding rather than by enhancing xylan binding. |
