Escherichia coli phosphoenolpyruvate-dependent phosphotransferase system: mechanism of phosphoryl-group transfer from phosphoenolpyruvate to HPr.
The mechanism of phosphoryl-group transfer from phosphoenolpyruvate (PEP) to HPr, catalyzed by enzyme I of the Escherichia coli PEP-dependent phosphotransferase system, has been studied in vitro. Steady-state kinetics and isotope exchange measurements revealed that this reaction cannot be described by a classical ping-pong mechanism although phosphoenzyme I acts as an intermediate. The kinetic data indicate that HPr and PHPr occupy binding sites on enzyme I that do not overlap with the binding sites for PEP and pyruvate. As a result, binding interactions between HPr and enzyme I exist regardless of their phosphorylated state. A general mechanism is presented that describes the phosphorylation of HPr. The physiological implications of this mechanism are discussed.
D004926:Escherichia coli / Q000201:enzymology*; D007700:Kinetics; D008433:Mathematics; D009097:Multienzyme Complexes / Q000378:metabolism; D010728:Phosphoenolpyruvate; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding
D009097:Multienzyme Complexes; D010728:Phosphoenolpyruvate; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System