| Title | Biocatalytic Properties and Substrate-binding Ability of a Modular GH10 β-1,4-Xylanase from an Insect-symbiotic Bacterium, Streptomyces mexicanus HY-14 |
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| Author | Do Young Kim1, Dong-Ha Shin2,3, Sora Jung1, Jong Suk Lee4, Han-Young Cho1, Kyung Sook Bae5, Chang-Keun Sung3, Young Ha Rhee6, Kwang-Hee Son1*, and Ho-Yong Park1* |
| Address | 1Industrial Bio-materials Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon 305-806, Republic of Korea, 2Insect Biotech Co. Ltd., Daejeon 305-811, Republic of Korea, 3Department of Food Science and Technology, Chungnam National University, Daejeon 305-764, Republic of Korea, 4Gyeonggi Bio-Center, Gyeonggi Institute of Science & Technology Promotion, Suwon 443-270, Republic of Korea, 5Microbial Resource Center, KRIBB, Daejeon 305-806, Republic of Korea, 6Department of Microbiology and Molecular Biology, Chungnam National University, Daejeon 305-764, Republic of Korea |
| Bibliography | Journal of Microbiology, 52(10),863-870, 2014, |
| DOI | 10.1007/s12275-014-4390-8 |
| Key Words | Streptomyces mexicanus HY-14, β-1,4-xylanase, GH family 10, modular enzyme, binding ability |
| Abstract | The gene (1350-bp) encoding a modular β-1,4-xylanase (XylU), which consists of an N-terminal catalytic GH10 domain and a C-terminal carbohydrate-binding module 2 (CBM 2), from Streptomyces mexicanus HY-14 was cloned and functionally characterized. The purified His-tagged recombinant enzyme (rXylU, 44.0 kDa) was capable of efficiently hydrolyze diverse xylosidic compounds, p-nitrophenyl-cellobioside, and pnitrophenyl- xylopyranoside when incubated at pH 5.5 and 65°C. Especially, the specific activities (649.8 U/mg and 587.0 U/mg, respectively) of rXylU toward oat spelts xylan and beechwood xylan were relatively higher than those (<500.0 U/mg) of many other GH10 homologs toward the same substrates. The results of enzymatic degradation of birchwood xylan and xylooligosaccharides (xylotriose to xylohexaose) revealed that rXylU preferentially hydrolyzed the substrates to xylobiose (>75%) as the primary degradation product. Moreover, a small amount (4%<) of xylose was detected as the degradation product of the evaluated xylosidic substrates, indicating that rXylU was a peculiar GH10 β-1,4- xylanase with substrate specificity, which was different from its retaining homologs. A significant reduction of the binding ability of rXylU caused by deletion of the C-terminal CBM 2 to various insoluble substrates strongly suggested that the additional domain might considerably contribute to the enzyme-substrate interaction. |