Bacterial phosphotransferase system: regulation of mannitol enzyme II activity by sulfhydryl oxidation.
The mechanism by which the oxidation-reduction potential regulates the bacterial phosphotransferase system in Escherichia coli has been investigated. Transphosphorylation experiments verified that the oxidizing agent, potassium ferricyanide, directly inhibits mannitol enzyme II activity. Phosphorylation of enzyme IImtl with enzyme I, heat-stable phosphocarrier protein of the phosphotransferase system, and phosphoenolpyruvate partially protects the enzyme from ferricyanide inhibition. The enzyme is even less sensitive to inhibition during catalytic turnover. Preincubation of unphosphorylated enzyme with ferricyanide, however, reversibly inactivates it even at high mannitol concentrations. The results are inconsistent with a regulatory mechanism in which sulfhydryl oxidation influences the affinity of the enzyme for the substrate. Instead, it is concluded that the oxidized enzyme is inactive.
D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins; D005292:Ferricyanides / Q000494:pharmacology; D007700:Kinetics; D009004:Monosaccharide Transport Proteins; D010084:Oxidation-Reduction; D010728:Phosphoenolpyruvate / Q000378:metabolism; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000378:metabolism*; D010766:Phosphorylation; D013438:Sulfhydryl Compounds
D029968:Escherichia coli Proteins; D005292:Ferricyanides; D009004:Monosaccharide Transport Proteins; D013438:Sulfhydryl Compounds; D010728:Phosphoenolpyruvate; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; C022358:mannitol PTS permease, E coli; C028033:potassium ferricyanide