Purification and characterization of extracellular and cell wall bound beta-glucosidases from Aspergillus kawachii.

Abstract

We isolated two extracellular beta-glucosidases (EX-1: 145 kDa, EX-2: 130 kDa) and one cell wall bound beta-glucosidase (CB-1: 120 kDa) from Aspergillus kawachii and characterized their physical and kinetic properties. From the results of N-terminal amino acid sequence, enzymatic parameters and deglycosylation of the three purified enzymes, we strongly suggest that these three enzymes were products of the same gene, modified by different degree of glycosylation. All three purified beta-glucosidases adsorbed to the purified cell wall fraction of this strain. This association could dramatically improve the stability of purified enzymes. These three purified beta-glucosidases were readily inactivated even in moderate conditions but became very stable upon the addition of the purified cell wall fraction. The all purified beta-glucosidases were stable in the range of pH 2.0-9.0 and stable below 30 degrees C with 2 mg/ml of the purified cell wall fraction.