The equilibrium constants of the adenosine triphosphate hydrolysis and the adenosine triphosphate-citrate lyase reactions.

The observed standard free energy change (AGibs) for the hydrolysis of the terminal pyrophosphate bond of ATP has been experimentally determined under physiological conditions using an entirely new set of reactions. The observed equilibrium constant (K,,bs) for the combined reactions of acetate kinase (EC 2.7.2.1) and phosphate acetyltransferase (EC 2.3.1.8) has been determined at 38”, pH 7.0, ionic strength 0.25, and varying free [Mg”+]. The K,,bs of these combined reactions reflects the difference between AG& for the hydrolysis of acetyl-CoA and the AGibs for the hydrolysis of ATP. Using 2 and square brackets to indicate total concentration,