Bacterial phosphoenolpyruvate-dependent phosphotransferase system. Mechanism of the transmembrane sugar translocation and phosphorylation.
The phosphoryl-group transfer from PHPr to glucose or alpha-methylglucose and from glucose 6-phosphate to these same sugars catalyzed by membrane-bound EIIBGlc of the bacterial phosphoenolpyruvate-dependent phosphotransferase system has been studied in vitro. Kinetic measurements revealed that both the phosphorylation reaction and the exchange reaction proceed according to a ping-pong mechanism in which a phosphorylated membrane-bound enzyme II acts as an obligatory intermediate. The occurrence of a phospho-IIBGlc/IIIGlc has been physically demonstrated by the production of a glucose 6-phosphate burst from membranes phosphorylated by phosphoenolpyruvate, HPr, and EI. The observation of similar second-order rate constants for the production of sugar phosphate starting with different phosphoryl-group donors confirms the catalytic relevance of the phosphoenzyme IIBGlc intermediate. The in vitro results, together with data published by other investigators, have led to a model describing sugar phosphorylation and transport in vivo.
D001419:Bacteria / Q000378:metabolism; D001693:Biological Transport, Active; D019298:Glucose-6-Phosphate; D005958:Glucosephosphates / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008956:Models, Chemical; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000378:metabolism*; D010766:Phosphorylation; D011773:Pyruvates / Q000378:metabolism; D019289:Pyruvic Acid; D012486:Salmonella typhimurium / Q000378:metabolism*
D005958:Glucosephosphates; D011773:Pyruvates; D019298:Glucose-6-Phosphate; D019289:Pyruvic Acid; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System