The standard Gibbs free energy change of hydrolysis of ribose-1-phosphate

The standard Gibbs free energy change of hydrolysis of α-d-ribose 1-phosphate has been measured at pH 7.0, ionic strength 0.1 m, and 25 °C by combining the corresponding values of the two following reactions: adenosine + H2O ág adenine + ribose (ΔG0′ = −2.3 ± 0.1 kcal/mol), catalyzed by adenosine nucleosidase, and ribose 1-phosphate + adenine ág adenosine + Pi (ΔG0′ = −3.1 ± 0.1 kcal/mol), catalyzed by adenosine phosphorylase. The standard Gibbs free energy changes were calculated for both reactions from the equilibrium constant. A value of -5.4 ± 0.15 kcal/mol, comparable to that of other hemiacetal phosphoric esters, was obtained for the hydrolysis of ribose 1-phosphate.