Abstract
Twelve cellulase components and a Jl-glusosidase were extensively purified to essential homo-geneity from a commercial crude cellulase preparation from Trichoderma viride (Meicelase) by a multi-step procedure involving Amberlite CG-50 and DEAE-Sephadex A-50 column chromato-graphic fractionations, affinity chromatography, isoelectric focusing, and gel filtration on Bio-Gel P-100. The purified were designated as cellulases I-al, I-a2, I-a3, I-b1, I-b2, II-al, II-b, II-c, III-a2, III, and IV, and were judged to be homogeneous on polyacrylamide gel and SDS-polyacrylamide gel as well as ampholine electrophoresis. All purified cellulases were com-pletely free from jS-glucosidase. The physicochemical and enzymatic properties of the purified were studied in detail and compared with each other. Of the twelve cellulase components, cellulases II-b and III were found to be the key enzymes in the cellulase system of T, viride. The purified cellulase II-b possessed a potent ability to produce glucose specifically from /l-D-cellobiose through enzy-mic reversion and transcellobiosylation without any participation of /S-glucosidase. It was strongly suggested that cellulase II-b would play an important role in glucose production in the enzymatic degradation of native cellulose. On the other hand, the purified cellulase III showed a high level of glucose production from crystalline cellulose by a multi-step reaction involving condensation followed by hydrolysis. The purified cellulase III corresponded absolutely to the known cellobiohydrolase (CBH, EC 3. 2. 1. 91) fudging from its physicochemical properties and substrate specificities. Even though cellobiose was the predominant product in the initial hydrolysis stage, it was clearly demonstrated from the experimental results that cellulase III was not 1, 4-β-D-glucan cellobiohy-drolase (CBH) but rather essentially a glucose-forming enzyme. Consequently, so-called CBH does not exist, at least in the cellulase system of T. viride. Now, we present the proposed scheme of the cooperative action by cellulases from T. viride in converting native cellulose to glucose.
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