Change in the binding of hydrogen ions and magnesium ions in the hydrolysis of ATP

Abstract

The binding of hydrogen ions and magnesium ions by a biochemical reactant, like ATP, can be calculated by writing the binding polynomial (partition function) Q and taking the partial derivatives of log Q with respect to pH and pMg by use of a mathematical program in a personal computer. The change in binding of hydrogen ions and magnesium ions in a biochemical reaction, like the hydrolysis of ATP, can be calculated by taking the partial derivatives of log( K′/ K), where K′ is the apparent equilibrium constant and K is the equilibrium constant for a reference chemical reaction. These calculations can be checked by using the computer to calculate the mixed partial derivatives, which must be equal. The effects of pH, pMg, and ionic strength on the changes in binding in the hydrolysis of ATP are calculated. At 298.15 K, pH 7, pMg 3, and 0.25 M ionic strength, the hydrolysis of ATP to ADP and inorganic phosphate liberates 0.62 mol of hydrogen ions and 0.45 mol of magnesium ions into the medium.