Isolation and characterization of β-glucosidases from Aspergillus nidulans mutant USDB 1183

Two extracellular β-glucosidases (cellobiase, EC 3.2.1.21), I and II, from Aspergillus nidulans USDB 1183 were purified to homogeneity with molecular weights of 240,000 and 78,000, respectively. Both hydrolysed laminaribiose, β-gentiobiose, cellobiose, p-nitrophenyl-β-L-glucoside, phenyl-β-L-glucoside, o-nitrophenyl-β-L-glucoside, salicin and methyl-β-L-glucoside but not α-linked disaccharides. Both were competitively inhibited by glucose and non-competitively (mixed) inhibited by glucono-1,5-lactone. β-Glucosidase I was more susceptible to inhibition by Ag(+) and less inhibited by Fe(2+) and Fe(3+) than β-glucosidase II.