Thermodynamics and Kinetics of the Glyoxylate Cycle^†

Because the standard Gibbs energies of formation of all the species of reactants in the glyoxylate cycle are known at 298.15 K, it is possible to calculate the apparent equilibrium constants of the five reactions in the cycle in the pH range 5−9 and ionic strengths from 0 to 0.35 M. In making calculations on such a system, it is convenient to specify concentrations of coenzymes like NAD_ox and NAD_red because they are involved in many reactions and may be in steady states. Calculations are given for [NAD_ox] = 1000[NAD_red] and [NAD_ox] = 10[NAD_red]. Equilibrium compositions are calculated using computer programs when all the reactants are present initially and when only glyoxylate and CoA are present initially. The kinetics of the reactions in the glyoxylate cycle at specified concentrations of NAD_ox and NAD_red are calculated by numerical solution of the steady-state rate equations for the case where the reactant concentrations are below their Michaelis constants and only glyoxylate and CoA are present initially.