Characterization of an exocellular β-glucosidase from Debaryomyces pseudopolymorphus

When grown in complex media containing 20 g of cellobiose per litre, Debaryomyces pseudopolymorphus secreted a P-glucosidase. The synthesis of this enzyme was repressed by glucose. Most of the enzyme was concentrated in the supernatant, with only 10% of the total activity being cell associated. This beta-glucosidase (designated Dp-beta gl) was purified and shown to be a monomer with a native molecular mass of approximately 100,000 Da. It demonstrated optimal activity at a pH of 4 and, in the short term (no more than 2 h), at a temperature of 40 degrees C. Temperature-stability analysis revealed that the enzyme was labile at 50 degrees C and above. It had a strong affinity for cellobiose and maltose, and degraded larninarin. It was inhibited by Ca++, Zn++, Mg++ and acetic acid, but apparently not by glucose and ethanol. (c) 2005 Elsevier Inc. All rights reserved.