title: Enzyme I of the phosphoenolpyruvate: sugar phosphotransferase system of Escherichia coli. Purification to homogeneity and some properties.
abstract: Enzyme I of the phosphoenolpyruvate - sugar phosphotransferase system (PTS) has been purified to homogeneity from Escherichia coli. A merodiploid strain P650 which had an extra copy of the gene for enzyme I resulting in a twofold increase in the amount of activity was used. The enzyme is a dimer of 67 000 +/- 5000 molecular weight subunits. At low protein concentration and 4 degrees C the monomer predominates, while at room temperature the dimer predominates. At higher protein concentrations (2 to 10 mg) this reversible temperature-dependent association-dissociation is not found. Enzyme I has a pH optimum of pH 7.2, a Km for HPr of 9 +/- 3 microM, a Km for phosphoenolpyruvate of 0.18 +/- 0.04 mM, and kinetics that are consistent with a bi bi Ping-Pong mechanism. No allosteric regulation of kinetic activity has been found. The amino acid composition has been determined and the epsilon 1% 280 nm is 4.4. Evidence suggests that the phosphorylated form of enzyme I is more stable.
mesh_terms: D002455:Cell Division; D004926:Escherichia coli / Q000201:enzymology*; D006639:Histidine / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008956:Models, Chemical; D008970:Molecular Weight; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000302:isolation & purification / Q000378:metabolism*; D011487:Protein Conformation; D013696:Temperature
chemical_list: D006639:Histidine; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System