A cellulolytic fungus, YDJ14, was isolated from compost and identified as an Aspergillus sp. strain. Three extracellular β-
glucosidases, BGL-A1, BGL-A2, and BGL-A3, were separated using ultrafiltration,
ammonium sulfate fractionation, and High-Q chromatography. The molecular masses of the three
enzymes were estimated to be 100, 45, and 40 kDa, respectively, by SDS-PAGE. The optimum pH and temperature of BGL-A3 were 5.0 and 50°C, respectively, whereas the optimum pH and temperature of BGL-A1 and BGL-A2 were identical (4.0 and 60°C, respectively). The half-life of BGL-A3 at 70°C (2.8 min) was shorter than that of BGL-A1 and BGL-A2 (12.1 and 8.8 min, respectively). All three
enzymes preferred p-nitrophenyl-β-D-glucopyranoside (
pNPG) and hardly hydrolyzed
cellobiose, suggesting that these
enzymes were aryl β-
glucosidases. The Km of BGL-A3 (1.26 mM) for
pNPG was much higher than that of BGL-A1 and BGL-A2 (0.25 and 0.27 mM, respectively). These results suggested that BGL-A1 and BGL-A2 were similar in their enzymatic properties, whereas BGL-A3 differed from the two
enzymes. When
tilianin (a
flavone glycoside of
acacetin) was reacted with the three
enzymes, the inhibitory activity for
monoamine oxidase, a target in the treatment of
neurological disorders, was similar to that shown by
acacetin. We conclude that these
enzymes may be useful in the hydrolysis of
flavone glycosides to improve their inhibitory activities.