Properties of β-Glucosidase Purified from Clostridium thermocellum

Summary: A cell-bound β-glucosidase (β-d-glucoside glucohydrolase; EC 3.2.1.21) from Clostridium thermocellum was purified to apparent homogeneity. A molecular weight of about 43000 gel fluration of the native enzyme on Ultrogel AcA34. A constant ratio of aryl-β-glucosidase and cellcouse throughout purification, similar heat stabilities, pH profiles and sensitivity to different hiibitor and competitive inhibition of the aryl-β-gluosidase and the ± suggest that the same enzyme accounts for the aryl-βglucosidase and the ± ctivities. However, the affinity for cellobiose was very much lower than for ± β-d-glucoside. The β-glucosidase had maximum rates at pH 6.0 to 6.5 for ± The enzyme was specific for substrates with the β-configuration. particulary and β-1,2 linkages. The enzyme did not hydrolyse carboxymethylcellulose or cellulose, but hydrolysed cello-oligosaccharides. It was strongly inhibited by ± was sensitive to thiol reagents. When preparations of C. thermocellm ± with purified β-glucosidase, glucose was the predominant ± of ± and the rate of saccharification was increased.