Effect of C-6 Methylol Groups on Substrate Recognition of Glucose/Xylose Mixed Oligosaccharides by Cellobiose Dehydrogenase from the Basidiomycete Phanerochaete chrysosporium |
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| Authors: | Kiyohiko Igarashi Satoshi Kaneko Motomitsu Kitaoka Masahiro Samejima |
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| Affiliation: | 1. Department of Biomaterial Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo;2. VTT Technical Research Centre of Finland Ltd.;3. Department of Subtropical Biochemistry and Biotechnology, Faculty of Agriculture, University of the Ryukyus;4. Faculty of Agriculture, Niigata University;5. Food Research Institute, National Agriculture and Food Research Organization;6. Faculty of Engineering, Shinshu University |
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| Abstract: | Cellobiose dehydrogenase (CDH) is a flavocytochrome catalyzing oxidation of the reducing end of cellobiose and cellooligosaccharides, and has a key role in the degradation of cellulosic biomass by filamentous fungi. Here, we use a lineup of glucose/xylose-mixed β-1,4-linked disaccharides and trisaccharides, enzymatically synthesized by means of the reverse reaction of cellobiose phosphorylase and cellodextrin phosphorylase, to investigate the substrate recognition of CDH. We found that CDH utilizes β-D-xylopyranosyl-(1→4)-D-glucopyranose (Xyl-Glc) as an electron donor with similar K m and k cat values to cellobiose. β-D-Glucopyranosyl-(1→4)-D-xylopyranose (Glc-Xyl) shows a higher K m value, while xylobiose does not serve as a substrate. Trisaccharides show similar behavior; i.e., trisaccharides with cellobiose and Xyl-Glc units at the reducing end show similar kinetics, while the enzyme was less active towards those with Glc-Xyl, and inactive towards those with xylobiose. We also use docking simulation to evaluate substrate recognition of the disaccharides, and we discuss possible molecular mechanisms of substrate recognition by CDH. |
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| Keywords: | cellobiose dehydrogenase Phanerochaete chrysosporium flavin adenine dinucleotide docking simulation |
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