Characterization of a recombinant β-glucosidase from the thermophilic bacterium Caldicellulosiruptor saccharolyticus(ENZYMOLOGY, PROTEIN ENGINEERING, AND ENZYME TECHNOLOGY)

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A recombinant β-glucosidase from Caldicellulosiruptor saccharolyticus DSM 8903 with a specific activity of 13U/mg was purified by heat treatment and His-Trap affinity chromatography and identified as a single 54kDa band on SDS-PAGE. The molecular mass of the native enzyme was 108kDa as a dimer by gel filtration. β-Glucosidase showed optimum activity at pH5.5 and 70℃ for p-nitrophenyl (pNP)-β-D-glucopyranoside. The half-lives of the enzyme at 60, 70, and 80℃ were 250, 24.3, and 0.4h, respectively. The enzyme exhibited catalytic efficiency and specific activity for pNP-β-D-fucopyranoside, pNP-β-D-glucopyranoside, and pNP-β-D-galactopyranoside in decreasing order among aryl-β-glycosides, but not for aryl-α-glycosides. Cello-oligosaccharides from n=2 to 5 as substrates using 4mM each sugar and 3U/mg of enzyme were completely hydrolyzed to glucose at 70℃ within 16h.
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