title: The functional groups of the Mg-Ca ATPase from Escherichia coli.
abstract: The influence of hydrogen ion concentration on binding and conversion of MgATP and CaATP by membrane bound and solubilized ATPase from Escherichia coli has been investigated. The reaction of enzyme (E), hydrogen ion (H+), and substrate (S) procedes according to the following scheme, where Me is the metal ion and P is the product(s). (See article for formular). Within experimental error, the results obtained with membrane-bound and solubilized ATPase are identical. Changing the concentration of Mg2+ ions or replacement of Mg2+ by Ca2+ ions alters the dissociation constants Kb, KHMeATP, and Ka'. The kinetics and experiments with group-specific inhibitors suggest that integrity for amino, imidazole, tyrosyl, carboxyl, and arginyl residues is required for activity of membrane-bound and solubilized E. coli ATPase.
mesh_terms: D000251:Adenosine Triphosphatases / Q000032:analysis* / Q000037:antagonists & inhibitors; D001120:Arginine / Q000378:metabolism; D002118:Calcium / Q000494:pharmacology; D002462:Cell Membrane / Q000201:enzymology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004926:Escherichia coli / Q000201:enzymology*; D006863:Hydrogen-Ion Concentration; D007093:Imidazoles / Q000378:metabolism; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008433:Mathematics; D008956:Models, Chemical; D012995:Solubility; D014443:Tyrosine / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; D007093:Imidazoles; D014443:Tyrosine; D001120:Arginine; D000251:Adenosine Triphosphatases; D008274:Magnesium; D002118:Calcium