Biochemical Characterization of Two Thermostable Xylanolytic Enzymes Encoded by a Gene Cluster of Caldicellulosiruptor owensensis
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| Authors: | Shuofu Mi Xiaojing Jia Jinzhi Wang Weibo Qiao Xiaowei Peng Yejun Han |
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| Institution: | 1. National Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, China.; 2. Institute of Agro-food Science and Technology, Chinese Academy of Agricultural Sciences, Beijing, China.; 3. Shenyang Agricultural University, Shenyang, China.; Laurentian University, Canada, |
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| Abstract: | The xylanolytic extremely thermophilic bacterium Caldicellulosiruptor owensensis provides a promising platform for xylan utilization. In the present study, two novel xylanolytic enzymes, GH10 endo-β-1,4-xylanase (Coxyn A) and GH39 β-1,4-xylosidase (Coxyl A) encoded in one gene cluster of C.owensensis were heterogeneously expressed and biochemically characterized. The optimum temperature of the two xylanlytic enzymes was 75°C, and the respective optimum pH for Coxyn A and Coxyl A was 7.0 and 5.0. The difference of Coxyn A and Coxyl A in solution was existing as monomer and homodimer respectively, it was also observed in predicted secondary structure. Under optimum condition, the catalytic efficiency (k
cat/K
m) of Coxyn A was 366 mg ml−1 s−1 on beechwood xylan, and the catalytic efficiency (k
cat/K
m) of Coxyl A was 2253 mM−1 s−1 on pNP-β-D-xylopyranoside. Coxyn A degraded xylan to oligosaccharides, which were converted to monomer by Coxyl A. The two intracellular enzymes might be responsible for xylooligosaccharides utilization in C.owensensis, also provide a potential way for xylan degradation in vitro. |
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