title: Kinetic analyses of the sugar phosphate:sugar transphosphorylation reaction catalyzed by the glucose enzyme II complex of the bacterial phosphotransferase system.
abstract: The sugar phosphate:sugar transphosphorylation reaction catalyzed by the glucose Enzyme II complex of the phosphotransferase system has been analyzed kinetically. Initial rates of phosphoryl transfer from glucose-6-P to methyl alpha-glucopyranoside were determined with butanol/urea-extracted membranes from Salmonella typhimurium strains. The kinetic mechanism was shown to be Bi-Bi Sequential, indicating that the Enzyme II possesses nonoverlapping binding sites for sugar and sugar phosphate. Binding of the two substrates appears to occur in a positively cooperative fashion. A mutant with a defective glucose Enzyme II was isolated which transported methyl alpha-glucoside and glucose with reduced maximal velocities and higher Km values. In vitro kinetic studies of the transphosphorylation reaction catalyzed by the mutant enzyme showed a decrease in maximal velocity and increases in the Km values for both the sugar and sugar phosphate substrates. These results are consistent with the conclusion that a single Enzyme II complex catalyzes both transport and transphosphorylation of its sugar substrates.
mesh_terms: D001692:Biological Transport; D005947:Glucose / Q000378:metabolism; D005958:Glucosephosphates / Q000378:metabolism; D007700:Kinetics; D008757:Methylglucosides / Q000378:metabolism; D009097:Multienzyme Complexes / Q000378:metabolism*; D009154:Mutation; D010728:Phosphoenolpyruvate; D010766:Phosphorylation; D010770:Phosphotransferases / Q000378:metabolism*; D012486:Salmonella typhimurium / Q000201:enzymology*; D013045:Species Specificity
chemical_list: D005958:Glucosephosphates; D008757:Methylglucosides; D009097:Multienzyme Complexes; D010728:Phosphoenolpyruvate; D010770:Phosphotransferases; D005947:Glucose