Abstract
The nature of the decomposition products of adenosine-5'-triphosphate (ATP) and the kinetics of decomposition in aqueous solution were investigated at 60, 70 and 80°C, ionic strength 0.5, pH 3.2-10.1 by high pressure liquid chromatography. Adenosine-5'-diphosphate (ADP) and adenoside-5'-monophosphate (AMP) were identified as the decomposition products of ATP. The time courses of the ATP and ADP concentrations were measured and the apparent 1st-order rate constants of the decomposition of ATP to ADP (k1), ADP to AMP (k2) and ATP to AMP (k3) were calculated. The order of decomposition rates was k1>k2>k3 in the pH range of 3.2-10.1. The observed decomposition rates of ATP and ADP were influenced significantly by spontaneous or water-catalyzed reaction. The specific rate constants of the ionic species of ATP and ADP were calculated, and it was found that decomposition rate of ATP including its decomposition products could be expressed by the summation of the products of the specific rate constants and mole fractions of the ionic species. The Arrhenius plots of these specific rate constants were linear and the apparent activation energies were all in the range of 28.8-31.8 kcal/mol. The primary salt effects on the decomposition of ATP were almost negligible. Therefore the overall decomposition rate of ATP including its decomposition products could be expressed as a function of the specific rate constants at arbitrary pH, temperature and ionic strength in several buffer species.
