Purification and characterization of β-1,4-glucosidase from Aspergillus glaucus

A beta-1,4-glucosidase (BG) was purified from fermentation liquor of Aspergillus glaucus by the following procedures: Ammonium sulfate precipitation, gel filtration on Sephadex G-100, and hydrophobic chromatography on Phenyl Sepharose Fast Flow. The specific activity on salicin was determined as 1747.4 U/mg. The molecular weight of this enzyme was determined as 23.5 and 92.5 kDa with SDS-PAGE and gel filtration on Sephadex G-100, respectively indicating that BG is a tetramer. The enzyme was stable at the pH ranging from 2.2 to 7.5, and its maximum activity was obtained at pH 3.6. The enzymatic activity gradually increased in the range from 40 to 60 degrees C, but a sharp decrease occurred at 65 degrees C. Enzymatic kinetics indicated that Michaelis-Menten contant (K-m) of the hydrolysis for salicin by BG was 2.58 mmol/L (pH 3.6, 60 degrees C). Na+, K+, Ca2+, Mg2+, Ba2+, NO3- and SO42- had no effects on BG activity. The enzyme activity was activated by Mn2+ and Fe2+, while it was strongly inhibited by Cu2+, Pb2+, Cd2+, SDS and EDTA, and slightly inhibited by Zn2+.