INDUCTION AND PRELIMINARY CHARACTERIZATION OF INTRACELLULAR BETA-GLUCOSIDASES FROM A CELLULOLYTIC STREPTOMYCES STRAIN

The cellulolytic actinomycete Streptomyces sp. QM-B814 posesses an int racellular beta-glucosidase system which is induced by cellobiose and carboxymethylcellulose. Maximal beta-glucosidase activity was attained 8-10 h after inducer addition to exponential phase growing cultures. The induction is depressed in the presence of glucose. The system is c omposed of two electrophoretically different beta-glucosidase forms sh owing relative molecular masses of about 60 and 35 kDa, and pI values in the range 4.2-4.5. Both beta-glucosidases are synthesized de novo. The enzymes share substrate preference and are both inhibited by delta -gluconolactone and p-chloromercuribenzoate. The induction pattern and glucose inhibition are similar for both enzymes.