Purification and properties of the cellulases from the thermophilic fungus Thermoascus aurantiacus

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Abstract
Three cellulases and a .beta.-glucosidase were purified from the culture filtrate of the thermophilic fungus T. aurantiacus. The isolated enzymes were all homogeneous on polyacrylamide-disc-gel electrophoresis. Data from chromatography on Bio-Gel P-60 and sodium dodecyl sulfate/polyacrylamide-gel electrophoresis indicated MW of 87,000 (.beta.-glucosidase), 78,000 (cellulase I), 49,000 (cellulase II) and 34,000 (cellulase III); the carbohydrate contents of the enzymes were 33.0, 5.5, 2.6 and 1.8% (wt/wt), respectively. Although the 3 purified cellulases were active towards filter paper, only cellulases I and III were active towards CM(carboxymethyl)-cellulose. Cellulase I was also active towards yeast glucan. The Km and catalytic-center-activity values for the enzymes were as follows: 0.52 .mu.mol/ml and 6.5 .times. 104 for .beta.-glucosidase on p-nitrophenyl .beta.-D-glucoside, 3.9 mg/ml and 6.3 for cellulase I on CM-cellulose, 1.2 mg/ml and 1.1 for cellulase I on yeast glucan, 34.4 mg/ml and 0.34 for cellulase II on filter paper, and 1.9 mg/ml and 33 for cellulase III on CM-cellulose.