GENETIC CONTROL OF β-GLUCOSIDASE SYNTHESIS IN SACCHAROMYCES LACTIS

Herman, Alberta (University of Wisconsin, Madison) and Harlyn Halvorson . Genetic control of β-glucosidase synthesis in Saccharomyces lactis . J. Bacteriol. 85: 901–910. 1963.—Both methyl-β- d -glucoside (2 × 10 −2 m ) and glucose (10 −3 m ) induced β-glucosidase synthesis in selected strains of Saccharomyces lactis . Genetic studies indicated the existence of a single locus specifically affecting β-methyl glucoside inducibility. Glucose-induced β-glucosidase synthesis, on the other hand, was nonspecific (other carbohydrases were simultaneously induced) and appeared to be controlled by more than one genetic factor. In both cases, noninducibility was dominant in diploids. The independent expression of these two modes of induction implied that these loci regulated β-glucosidase induction in a nonsequential manner.

IDENTIFICATION OF THE STRUCTURAL GENE FOR β-GLUCOSIDASE IN SACCHAROMYCES LACTIS

Herman, Alberta (University of Wisconsin, Madison) and Harlyn Halvorson . Identification of the structural gene for β-glucosidase in Saccharomyces lactis . J. Bacteriol. 85: 895–900. 1963.—Three allelic forms (B h, m, l ) of the structural gene for β-glucosidase have been identified in the yeast Saccharomyces lactis . Evidence that these are structural gene alleles includes the independent expression of the alleles in homozygous and heterozygous diploids and differences in the specificity and in the physical properties of the enzyme produced in response to the various allelic mutations. Two factors, one controlling production of the pulcherrimin-like pigment, the other β-galactosidase activity, are linked to the B locus. The β-glucosidase in these strains hydrolyzes the chromogenic substrate, p -nitrophenyl-β- d -glucoside, arbutin, salicin, and esculin. Cellobiose, on the other hand, is hydrolyzed by another enzyme.