The use of transition state acid dissociation constants in pH-dependent enzyme kinetics

It is shown that the variation of reaction rate with pH in systems where several protonated forms of the reactants appear to be kinetically active may be expressed most economically in terms of transition state acid dissociation constants. The advantages of this approach are described in relation to the formal analysis of experimental data with regard to both simple and complex reactions and the satisfaction of the principle of microscopic reversibility. Ligand binding to metmyoglobin is used to illustrate the value of the approach in searching for detailed mechanistic explanations.