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-bin ding parameters for competitive dead-end inhibitors for the yeast alcohol d ehydrogenase (EC 1.1.1.1, constitutive, cytoplasmic) reaction was studied i n the pH range 6-10. These studies were designed in order to assign the app ropriate pK(a), values to all dissociation forms of enzyme in the chemical mechanism of action for the yeast enzyme, previously proposed by Cook and C leland [P.F Cook & W. W. Cleland (1981) Biochemistry 20, 1796-1816]. Tn add ition, the chemical mechanism of action for the yeast enzyme, proposed in t his work, was compared with a similar mechanism of action for the horse liv er enzyme, proposed by Cook and Cleland. Substantial differences were found , especially in the binding of coenzymes and in the structure of enzyme-coe nzyme complexes.