title: Effect of galactose on beta-galactosidase synthesis in Escherichia coli K-12.
abstract: In wild-type strains of Escherichia coli K-12, the rate of thiomethylgalactoside (TMG)-induced beta-galactosidase synthesis is decreased in the presence of galactose or glucose. A spontaneous mutant of a K-12 strain, 58-161, which synthesizes beta-galactosidase at a low rate was isolated. In this mutant, galactose, after a lag of about one generation time, evoked the same final differential rate of enzyme synthesis as did the gratuitous inducer TMG. However, constitutive, TMG-induced and galactose-induced synthesis in the mutant were subject to inhibition by exogenous glucose. It is concluded that repression of beta-galactosidase synthesis derived from glucose is distinct from the inhibition derived from galactose.
mesh_terms: D004790:Enzyme Induction; D004794:Enzyme Repression; D004926:Escherichia coli / Q000201:enzymology*; D005690:Galactose / Q000494:pharmacology*; D005696:Galactosidases / Q000096:biosynthesis*; D005947:Glucose / Q000494:pharmacology; D007700:Kinetics; D009154:Mutation; D013997:Time Factors
chemical_list: D005696:Galactosidases; D005947:Glucose; D005690:Galactose