title: HPr/HPr-P phosphoryl exchange reaction catalyzed by the mannitol specific enzyme II of the bacterial phosphotransferase system.
abstract: The mannitol specific Enzyme II of the phosphoenolpyruvate: sugar phosphotransferase system of Escherichia coli catalyzes an exchange reaction in which a phosphoryl moiety is transferred from one molecule of the heat stable phosphocarrier protein HPr to another. An assay was developed for measuring this reaction. Unlabeled phospho-HPr and 125I-labeled free HPr were incubated together in the presence of Enzyme IImtl, and production of 125I-labeled phospho-HPr was measured. The reaction was concentration-dependent with respect to Enzyme IImtl and did not occur in its absence. The reaction occurred in the absence of Mg2+ in the presence of 10 mM EDTA. Treatment of Enzyme IImtl with the histidyl reagent diethylpyrocarbonate inactivated it with respect to the exchange reaction. Levels of N-ethylmaleimide which inactivate Enzyme IImtl with respect to both P-enolpyruvate-dependent phosphorylation of mannitol and mannitol/mannitol-1-P transphosphorylation did not affect its activity in the exchange reaction; however, treatment with another sulfhydryl reagent, p-chloromercuribenzoate, resulted in partial inactivation. The pH optimum for the Enzyme IImtl-catalyzed exchange reaction was about 7.5. Enzyme I and the glucose specific Enzyme III, two other E. coli phosphotransferase system proteins which, like Enzyme IImtl, interact directly with HPr, were also shown to catalyze 125I-HPr/HPr-P phosphoryl exchange.
mesh_terms: D001426:Bacterial Proteins; D004047:Diethyl Pyrocarbonate / Q000494:pharmacology; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins; D005033:Ethylmaleimide / Q000494:pharmacology; D008274:Magnesium / Q000378:metabolism; D008353:Mannitol / Q000378:metabolism; D008355:Mannitol Phosphates / Q000378:metabolism; D009004:Monosaccharide Transport Proteins; D010728:Phosphoenolpyruvate / Q000378:metabolism; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000378:metabolism*; D010766:Phosphorylation
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D008355:Mannitol Phosphates; D009004:Monosaccharide Transport Proteins; C030070:mannitol-1-phosphate; D008353:Mannitol; D010728:Phosphoenolpyruvate; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; C022358:mannitol PTS permease, E coli; C030182:phosphocarrier protein HPr; D008274:Magnesium; D004047:Diethyl Pyrocarbonate; D005033:Ethylmaleimide