title: Hypothesis--a chemical mechanism for the biosynthesis of ATP involving ion-exchange reactions.
abstract: Dissociation constants for Mg . ATP were determined by displacing ATP from Dowex-1 resin with magnesium. These constants were then used to analyze the kinetics of yeast mitochondrial ATPase, in terms of the concentrations of free magnesium and free ATP, at a series of pH values. Both Mg . ATP and hydroxide ions were found to compete with the binding of ATP to the enzyme. These results were interpreted, in terms of an ion-exchange model, to mean that the synthesis of ATP may require the utilization of both magnesium and hydroxide ions for the dissociation of ATP from the enzyme as Mg . ATP. The concentrations of Mg and hydroxide required to compete with ATP were both found to be about three orders of magnitude greater than those required to form products, indicating that magnesium and hydroxide ions can contribute about 8 kcal of energy when ATP is synthesized.
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000096:biosynthesis* / Q000378:metabolism; D000837:Anion Exchange Resins; D001667:Binding, Competitive; D002413:Cations, Divalent; D006863:Hydrogen-Ion Concentration; D006878:Hydroxides / Q000378:metabolism; D007474:Ion Exchange; D007700:Kinetics; D008274:Magnesium / Q000378:metabolism; D008956:Models, Chemical; D011485:Protein Binding; D013816:Thermodynamics
chemical_list: D000837:Anion Exchange Resins; D002413:Cations, Divalent; D006878:Hydroxides; D000255:Adenosine Triphosphate; C031356:hydroxide ion; D000251:Adenosine Triphosphatases; D008274:Magnesium