摘要：C -Glucosides, in which sugars are attached to the aglycone by carbon–carbon bonds, are generally resistant to acid and enzyme hydrolysis. The C -glucosyl bond of mangiferin, a xanthone C -glucoside, was cleaved by anaerobic incubation with a human intestinal bacterium, Bacteroides sp. MANG, to give norathyriol. A cell-free extract obtained by sonication of B. sp. MANG demonstrated cleaving activity for mangiferin to norathyriol by adding NADH, diaphorase, and dithiothreitol. Both high molecular weight (>10 k) and low molecular weight (<10 k) fractions obtained from the cell-free extract were required for the activity. MnCl2 was necessary for the activity, but other metal ions were not. By purification of the high molecular weight fraction using DEAE-cellulose and Phenyl Sepharose column chromatography, two fractions, designated as proteins A and B, were separated and required for the activity. Neither protein A nor protein B alone showed any activity. This is the first report describing a C -glucosyl-cleaving enzyme from human intestinal bacterium that seems to involve a novel enzyme mechanism.
