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 β-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 β-glucosidase (designated Dp-βgl) 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 °C. Temperature-stability analysis revealed that the enzyme was labile at 50 °C and above. It had a strong affinity for cellobiose and maltose, and degraded laminarin. It was inhibited by Ca++, Zn++, Mg++ and acetic acid, but apparently not by glucose and ethanol.