Purification and Characterization ofβ- D -Glucosidase (β- D -Fucosidase) fromBifidobacterium breveclb Acclimated to Cellobiose

The beta-D-glucosidase (EC. 3.2.1.21) activity of Bifidobacterium breve 203 was increased by acclimation with cellobiose, and the enzyme was purified to homogeneity from cell-free extracts of an acclimatized strain of B. breve clb, by ammonium sulfate fractionation and column chromatographies of anion-exchange, gel filtration, Gigapaite, and hydrophobic interaction. This enzyme had not only beta-D-glucosidase activity but also beta-D-fucosidase activity, which is specific to Bifidobacteria in intestinal flora. The molecular weight of the purified enzyme was estimated to be 47,000-48,000 and the enzyme was assumed to be a monomeric protein. The optimum pH and temperature of the enzyme were around 5.5 and 45 degrees C, respectively. The enzyme was stable up to 40 degrees C and between pH 5 and 8. The isoelectric point of the enzyme was 4.3 and the Km values for p-nitrophenyl-beta-D-glucoside and p-nitrophenyl-beta-D-fucoside were 1.3 mM and 0.7 mM, respectively. This enzyme had also transferase activity for the beta-D-fucosyl group but not for the beta-D-glucosyl group. The N-terminal amino acid sequence of this enzyme was similar to those of beta-D-glucosidase from other bacteria, actinomycetes, and plants.