SUMMARY: The β--glucosidase which was associated with the cellobiohydrolase and endo-(1·4)-β--glucanase activities in the cellulase of the fungus was purified by gel filtration on a column of Ultrogel AcA 44, ion-exchange chromatography on DEAE-Sepharose and sulphoethyl-Sephadex (SE-Sephadex), and finally by isoelectric focusing in a pH gradient supported in a sucrose density gradient. The separation of β-glucosidase and endo-(l·4)-β-glucanase, which was effected with some difficulty on SE-Sephadex, could be achieved readily by chromatography on a column of concanavalin A-Sepharose. Isoelectric focusing yielded two β-glucosidase components (pI 5·53 and 5·85) of identical molecular weight (39800), but with different affinities for -nitrophenyl-β-glucoside ( 0·37 · 0·04 and 0·85 · 0·3 m), cellobiose ( 1·18 · 0·09 and 0·86 · 0·02m) cellotriose ( 5·10 · 0·22 and 7·10 · 0·33 m), cellotetraose ( 2·38 · 0·14 and 4·0 · 0·4m) and cellopentaose ( 1·51 · 0·04 and 2·19 · 0·06 m). One of the β-glucosidases was devoid of carbohydrate, the other contained approximately 2% carbohydrate. Gluconolactone was a powerful inhibitor of the action of both enzymes on -nitrophenyl-β-glucoside ( 1·8 · 0·08 and 1·17 · 0·05 μ); glucose was less effective ( 1·05 · 0·07 and 0·66 · 0·04 m). Inhibition was of the competitive type in each case. Both β-glucosidases showed the same capacity for acting in synergism with a mixture of the endo-(l·4)-β-glucanase and cellobiohydrolase in solubilizing the cellulose in cotton fibre. They differed markedly, however, in the degree of synergism they showed when acting in concert with the cellobiohydrolase on partially degraded HPO-swollen cellulose.


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