Purification and characterization of ginsenoside Ra-hydrolyzing beta-D-xylosidase from Bifidobacterium breve K-110, a human intestinal anaerobic bacterium.

Beta-D-Xylosidase (EC 3.2.1.37) has been purified from ginsenoside Ra-metabolizing Bifidobacterium breve K-110, which was isolated from human intestinal microflora. beta-D-Xylosidase was purified to apparent homogeneity by a combination of ammonium sulfate precipitation, QAE-cellulose, butyl-toyopearl, hydroxyapatit and Q-Sepharose column chromatographies with the final specific activity of 51.8 micromol/min/mg. Molecular weight of beta-D-xylosidase is 49 kDa by SDS-PAGE and gel filtration, which consisted of a single subunit. beta-D-Xylosidase showed optimal activity at pH 5.0 and 37 degrees C. The purified enzyme was potently inhibited by PCMS. beta-D-Xylosidase acted to the greatest extent on p-nitrophenyl-beta-D-xylopyranoside, followed by ginsenoside Ra1 and ginsenoside Ra2. This enzyme hydrolyzed xylan to xylose, but did not act on p-nitrophenyl-beta-glucopyranoside, p-nitrophenyl-beta-galactopyranoside or p-nitrophenyl-beta-D-fucopyranoside. These findings suggest that this is the first reported purification of ginsenoside-hydrolyzing beta-D-xylosidase from an anaerobic Bifidobacterium sp.