CHARACTERIZATION OF AN INTRACELLULAR BETA-GLUCOSIDASE FROM STREPTOMYCES-RETICULI

Streptomyces reticuli hydrolyzes cellobiose to glucose by mycelia-associated, extra- and intracellular beta-glucosidase activities during cultivation with crystalline cellulose (Avicel) or cellobiose as carbon source. One intracellular beta-glucosidase was purified to near homogeneity by the use of a fast protein liquid chromatography system combined with several ion-exchange and hydrophobic-interaction columns. The unglycosylated enzyme has an apparent molecular weight of 50 kDa and an isoelectric point of 4.5, and shows optimal activity at pH 7 and 40-degrees-C. It can be stimulated by CaCl2, MgSO4, or cellobiose, and is inhibited by glucose, glucono-lactone, or histidine, but not by imidazole. The beta-glucosidase hydrolyzes p-nitrophenyl-beta-D-gluco-pyranoside, cellobiose, and cellodextrins. The release of glucose from cellooligomers decreases in proportion to their lengths.