Induction of beta-glucosidases in Neurospora crassa

The induction of beta-glucosidases (EC 3.2.1.21) was studied in Neurospora crassa. Cellobiase was induced by cellobiose, but other inducers had little effect on this enzyme. Cellobiase activity was very low in all stages of the vegetative life cycle in the absence of di-beta-glucoside inducer. Aryl-beta-glucosidase was semiconstitutive at late stages of culture growth prior to conidiation. At early stages, aryl-beta-glucosidase was induced by cellobiose, laminaribiose, and gentiobiose, and weakly induced by galactose, amino sugars, and aryl-beta-glucosides. The induction properties of the beta-glucosidases are compared with those of the other disaccharidases of Neurospora. The induction of beta-glucosidases was inhibited by glucose, 2-deoxy-d-glucose, and sodium acetate. Sodium phosphate concentrations between 0.01 and 0.1 M stimulated induction of both enzymes, while concentrations above 0.1 M were inhibitory. The optimal condition for induction of both beta-glucosidases was pH 6.0. Cellobiase induction was relatively more inhibited than aryl-beta-glucosidase in the range of pH 6.0 to 8.0.