A species of the imperfect fungus produced extracellular, intracellular and mycelial-bound β-glucosidases when grown on cellulose. The extracellular enzyme was induced on cellulose but was repressed by cellobiose and glucose. Derepression of this enzyme occurred when cellobiose and glucose were nearly exhausted from the growth medium. Intracellular and mycelial-bound β-glucosidases were induced on cellulose and cellobiose but appeared to be repressed on glucose and lactose. One extracellular (EG-1) and two intracellular (IG-1, IG-2) β-glucosidases were produced when sp. was grown on cellulose. The molecular weights of EG-1 and IG-2 were 37500 and that of IG-1 was 480000. The of EG-1 and IG-2 was 8 x 10 M for -nitrophenyl-β-D-glucoside (PNPG), and 5.7 x 10 M for cellobiose; the for glucose, a competitive inhibitor, was 6.7 x 10 M. The of IG-1 was 1.67 x 10 M for PNPG and 2.0 x 10 M for cellobiose; the for glucose, a non-competitive inhibitor, was 1.63 x 10 M. β-Glucosidases EG-1 and IG-2 showed optimal activity at pH4.5 whilst the pH optimum for IG-1 was 4.2. Temperature optima were 50 C for EG-1 and IG-2, and 60-65 C for IG-1. Their respective isoelectric points were 8.3, 8.3 and 4.4.


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