Beta-xylosidase activity of a GH3 glucosidase/xylosidase from yak rumen metagenome promotes the enzymatic degradation of hemicellulosic xylans.

作者: J. Zhou , L. Bao , L. Chang , Z. Liu , C. You

DOI: 10.1111/J.1472-765X.2011.03175.X

关键词: Glycoside hydrolase family 3CelluloseHydrolysisBiochemistryHydrolaseXylanXylobioseBiologyXyloseXylooligosaccharide

摘要: Aims:  To characterize the duel activities of a glycosyl hydrolase family 3 β-glucosidase/xylosidase from rumen bacterial metagenome and to investigate capabilities its β-d-xylosidase for saccharification hemicellulosic xylans. Methods Results:  A gene RuBGX1 was cloned yak (Bos grunniens) using metagenomic technology. Recombinant RuBGX1, expressed in Escherichia coli, demonstrated high hydrolytic on both p-nitrophenyl-β-d-glucopyranoside (pNP-Glc) p-nitrophenyl-β-d-xylopyranoside (pNP-Xyl) substrates. Analysis kinetic properties indicated that had lower affinity pNP-Glc substrate as Km 0·164 mmol l−1 0·03 mmol l−1 pNP-Xyl at pH 6·0 50°C, respectively. The β-xylosidase hydrolysis xylooligosaccharide substrates were further investigated an endoxylanase-coupled assay. Hydrolysis time courses illustrated significant increase (about 50%) reducing sugars, including xylobiose, xylotriose xylotetraose, achieved by supplementing endoxylanase with RuBGX1. Enzymatic product analysis high-performance anion-exchange chromatography-pulsed amperometric detection showed could release xyloses intermediate xylooligosaccharides produced endoxylanase. Conclusions:  shows β-glucosidase activity cello-oligosaccharides; meanwhile, it has functions synergistically promote degradation xylans. Significance Impact study:  This first report functioned xylans. bifunctional property can be used simultaneous cellulose xylan into fermentable glucose xylose.

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