EFFECT OF BETA-GLUCOSIDASE INHIBITORS ON SYNTHESIS OF CELLULASE AND BETA-GLUCOSIDASE IN SPOROTRICHUM (CHRYSOSPORIUM) THERMOPHILE

The addition of nojirimycin or gluconolactam, substances known as beta-glucosidase inhibitors, to cultures of Sporotrichum (Chrysosporium) thermophile growing on cellobiose, caused a twofold or even higher increase (inhibited by cycloheximide) of the intracellular activity of this enzyme, but did not stimulate the synthesis of endocellulase or of cellobiose dehydrogenase. At concentrations from 0.1 to 1.0 mM, nojirimycin stimulated beta-glucosidase synthesis to an extent apparently independent of concentration but did not affect cellular respiration on cellobiose. At 5 mM, however, cellobiose assimilation and subsequent growth were significantly but only temporarily impaired and beta-glucosidase synthesis, which was still stimulated, was correspondingly delayed. Growth on glucose, on the other hand, was completely unaffected by nojirimycin. Upon fast protein liquid chromatography (FPLC) fractionation by gel filtration of mycelial extracts from cultures grown in the presence and in the absence of nojirimycin (0.1 mM), the beta-glucosidase was recovered (67-70%) in two distinct fractions, A and B. The observed increase in beta-glucosidase activity for cultures with nojirimycin was found to parallel the increase of fraction B.