Purification and characterization of ginsenoside Rb1-metabolizing β-glucosidase from Fusobacterium K-60, a human intestinal anaerobic bacterium

Fusobacterium K-60, a ginsenoside R-b1-metabolizing bacterium, was isolated from human intestinal feces. From this Fusodobacterium K-60, a ginsenoside R-b1-metabolizing enzyme, beta -glucosidase, has been purified. The enzyme was purified to apparent homogeneity by a combination of butyl-Toyopearl, hydroxyapatite ultragel, Q-Sepharose, and Sephacryl S-300 HR column chromatographies with a final specific activity of 1.52 mu mol/min/mg. It had optimal activity at pH 7.0 and 40 degreesC. The molecular mass of this purified enzyme was 320 kDa, with 4 identical subunits (80 kDa). The purified enzyme activity was inhibited by Ba++, Fe++, and some agents that modify cysteine residues. This enzyme strongly hydrolyzed sophorose, followed by p-nitrophenyl beta -D-glucopyranoside, esculin, and ginsenoside Rbl. However, this enzyme did not change 20-O-beta -D-glucopyranosyl-20(S)-protopanaxadiol (IH-901) to 20(S)-protopanaxadiol, while it weakly changed ginsenoside R-b1 to IH-901. These findings suggest that the Fusobacterial beta -glucosidase is a novel enzyme transforming ginsenoside R-b1.