Pea alcohol dehydrogenase: Substrate specificity and binding of coenzyme to enzyme

Abstract

Pea alcohol dehydrogenase (EC 1.1.1.1) shows a broad specificity with respect to aldehydes and alcohols. The pH-optimum of substrate oxidation is 8.7 and of substrate reduction 7.0. The enzyme is inhibited by ATP, adenosine, and adenine. The inhibition is competitive with respect to NAD. The inhibition by ATP is pH-dependent. The competitive character of the inhibition by adenine and its derivatives with respect to NAD indicates the importance of the adenine moiety of the coenzyme for its binding to the enzyme. Phenanthroline is a competitive inhibitor with respect to NAD, a mixed inhibitor with respect to ethanol and a noncompetitive inhibitor with respect to acetaldehyde. Experiments carried out simultaneously with ATP and phenanthroline show that the adenine moiety of NAD does not bind via the zinc atom to the enzyme protein.