title: Competition between two pathways for sugar uptake by the phosphoenolpyruvate-dependent sugar phosphotransferase system in Salmonella typhimurium.
abstract: The interaction between the two pathways for glucose entry via the phosphoenolpyruvate:sugar phosphotransferase system, i.e. via enzyme II-A/II-B and enzymes II-BGlc/IIIGlc, was studied in Salmonella typhimurium. Thio-beta-D-glucoside and 5-thio-D-glucose were shown to be substrates of P-pyruvate:sugar phosphotransferase specific for enzyme II-BGlc both in intact cells and in toluene-treated cells of S. typhimurium. The activity of the II-A/II-B pathway was strongly inhibited by the presence of II-BGlc substrates. It is concluded that the two pathways compete for phosphoryl groups provided by P-pyruvate, and that under the conditions tested the flow of phosphoryl groups through enzyme I/HPr is the rate-limiting step in vivo of activity of the pathways studied. The results corroborate the proposed mechanism of the regulatory function of the P-pyruvate:sugar phosphotransferase system which predicts a net dephosphorylation of components of the P-pyruvate:sugar phosphotransferase in the presence of a substrate of P-pyruvate:sugar phosphotransferase.
mesh_terms: D005947:Glucose / Q000031:analogs & derivatives / Q000378:metabolism*; D007700:Kinetics; D008358:Mannose / Q000378:metabolism; D008757:Methylglucosides / Q000378:metabolism; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000378:metabolism*; D010766:Phosphorylation; D012486:Salmonella typhimurium / Q000378:metabolism*; D013863:Thioglucosides / Q000378:metabolism
chemical_list: D008757:Methylglucosides; D013863:Thioglucosides; C003002:5-thio-D-glucose; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; D005947:Glucose; D008358:Mannose