Simultaneous binding of coenzyme-competitive inhibitors of yeast alcohol dehydrogenase

Abstract

Multiple inhibition studies of yeast alcohol dehydrogenase (alcohol:NAD oxidoreductase, E.C. I.I.I.I) were carried out using as inhibitor pairs various combinations of n-alkylammonium chlorides with adenylic acid and adenosine diphosphoribose, and N 1 -alkylnicotinamide chlorides with adenylic acid and adenosine diphosphoribose. Inhibitors interacting with the enzyme at the “pyridinium ring” region of the NAD binding site were demonstrated to be bound to the enzyme simultaneously with adenine derivatives. A pronounced positive interaction was observed in the simultaneous binding of adenine and nicotinamide derivatives, suggesting a possible ring-ring interaction in the positioning of these inhibitors on the enzyme. N 1 -Alkyl-nicotinamide chlorides are bound simultaneously with NADH to yeast alcohol dehydrogenase and do not effectively inhibit the enzyme-catalyzed reduction of acetaldehyde. The studies presented suggest a different mode of binding to yeast alcohol dehydrogenase for the oxidized and reduced pyridine moieties of the coenzymes, NAD and NADH.