Metabolic control of beta-glucosidase synthesis in yeast.

MacQuillan, Anthony M. (University of Wisconsin, Madison) and Harlyn O. Halvorson. Metabolic control of beta-glucosidase synthesis in yeast. J. Bacteriol. 84:23-30. 1962-The hybrid Saccharomyces fragilis x S. dobzhanskii produced a constitutive beta-glucosidase when grown in succinate synthetic medium. Upon addition of beta-glucosides, thio-beta-glucosides, or low concentrations of glucose, a further induction of enzyme synthesis was observed. Studies with other sugars revealed some specificity in response to hexose induction. Phenyl-thio-beta-d-glucoside did not affect constitutive synthesis nor induction by glucosides, thio-glucosides, or glucose. Repression of beta-glucosidase synthesis is brought about by high concentrations of glucose and other carbon compounds. Preinduction does not confer resistance to catabolic repression of enzyme synthesis; this leads to the conclusion that two sites of control for beta-glucosidase synthesis are present in yeast. Multiplicity of control is further suggested from: (i) the properties of the inducing system; (ii) semiconstitutive nature of enzyme synthesis; (iii) the repression of constitutive synthesis by glucose; (iv) the elevated derepressed rates of enzyme synthesis after glucose inhibition; and (v) the selection of a family of low constitutive mutants with variable inducibility.