PROPERTIES OF A NOVEL GLUCOSE-ENHANCED BETA-GLUCOSIDASE PURIFIED FROMSTREPTOMYCES SP (ATCC-11238)

An inducible intracellular beta-glucosidase (EC 3.2.1.21) from Strepto myces sp. QM-B814 (ATCC 11238) has been purified and characterized, Th e purified polypeptide is monomeric with a relative molecular mass of 62 kDa by SDS-PACE and 42 kDa by size-exclusion chromatography; its is oelectric point is 4.2, The difference in the molecular mass values ca n be attributed to the glycosylated nature of the protein. The purifie d enzyme has a pH optimum of 6.0-6.5. The temperature optimum for acti vity is 50 degrees C; at this temperature the enzyme is stable for 1 h . The enzyme hydrolyzes mainly aryl-beta-glucosides but also presents significant activity against beta-linked disaccharides and maltose. Th e enzyme displays an unusual kinetic behavior and biphasic Lineweaver- Burk and Eadie-Hofstee plots for p-nitrophenyl-beta-D-glucoside and ce llobiose were obtained. The enzyme presents beta-glycosyltransferase a ctivity and an exoglycosidase-type action on cellodextrins. It is inhi bited by delta-gluconolactone(K-i 0.44 mM) but, remarkably, glucose in the range 25-200 mM enhances the rate of p-nitrophenyl-beta-D-glucosi de hydrolysis.