Comparison of the chemical mechanisms of action of yeast and equine liver alcohol dehydrogenase.

The pH-dependence of the steady-state kinetic parameters and the ligand-binding parameters for competitive dead-end inhibitors for the yeast alcohol dehydrogenase (EC 1.1.1.1, constitutive, cytoplasmic) reaction was studied in the pH range 6-10. These studies were designed in order to assign the appropriate pKa values to all dissociation forms of enzyme in the chemical mechanism of action for the yeast enzyme, previously proposed by Cook and Cleland [P. F. Cook & W. W. Cleland (1981) Biochemistry 20, 1796-1816]. In addition, the chemical mechanism of action for the yeast enzyme, proposed in this work, was compared with a similar mechanism of action for the horse liver enzyme, proposed by Cook and Cleland. Substantial differences were found, especially in the binding of coenzymes and in the structure of enzyme-coenzyme complexes.