title: Relaxation of catabolite repression in streptomycin-dependent Escherichia coli.
abstract: Acetohydroxy acid synthetase, which is sensitive to catabolite repression in wild-type Escherichia coli B, was relatively resistant to this control in a streptomycin-dependent mutant. The streptomycin-dependent mutant was found to be inducible for beta-galactosidase in the presence of glucose, although repression of beta-galactosidase by glucose occurred under experimental conditions where growth of the streptomycin-dependent mutant was limited. Additional glucose-sensitive enzymes of wild-type E. coli B (citrate synthase, fumarase, aconitase and isocitrate dehydrogenase) were found to be insensitive to the carbon source in streptomycin-dependent mutants: these enzymes were formed by streptomycin-dependent E. coli B in equivalent quantities when either glucose or glycerol was the carbon source. Two enzymes, glucokinase and glucose 6-phosphate dehydrogenase, that are glucose-insensitive in wild-type E. coli B were formed in equivalent quantity on glucose or glycerol in both streptomycin-sensitive and streptomycin-dependent E. coli B. The results indicate a general decrease or relaxation of catabolite repression in the streptomycin-dependent mutant. The yield of streptomycin-dependent cells from glucose was one-third less than that of the streptomycin-sensitive strain. We conclude that the decreased efficiency of glucose utilization in streptomycin-dependent E. coli B is responsible for the relaxation of catabolite repression in this mutant.
mesh_terms: D002256:Carbonic Anhydrases / Q000378:metabolism; D004790:Enzyme Induction; D004794:Enzyme Repression; D004926:Escherichia coli / Q000201:enzymology*; D005696:Galactosidases / Q000378:metabolism; D005941:Glucokinase / Q000096:biosynthesis; D005947:Glucose / Q000378:metabolism; D005954:Glucosephosphate Dehydrogenase / Q000096:biosynthesis; D005990:Glycerol / Q000378:metabolism; D006836:Hydro-Lyases / Q000378:metabolism; D007521:Isocitrate Dehydrogenase / Q000378:metabolism; D008025:Ligases / Q000378:metabolism*; D008190:Lyases / Q000378:metabolism; D009154:Mutation; D013307:Streptomycin / Q000378:metabolism*
chemical_list: D007521:Isocitrate Dehydrogenase; D005954:Glucosephosphate Dehydrogenase; D005941:Glucokinase; D005696:Galactosidases; D008190:Lyases; D006836:Hydro-Lyases; D002256:Carbonic Anhydrases; D008025:Ligases; D005947:Glucose; D005990:Glycerol; D013307:Streptomycin