Sulfhydryl enzyme inactivation by nicotinoylacrylates

Abstract

Nicotinoylacrylic acid and the corresponding methyl, ethyl, propyl and benzyl esters were studied with respect to selective inactivation of dehydrogenases through covalent modification of essential sulfhydryl groups. An effective inactivation of yeast alcohol dehydrogenase, yeast glutathione reductase and yeast 6-phosphogluconate dehydrogenase was observed with methyl and ethyl nicotinoylacrylates, with nicotinoylacrylic acid and the larger propyl and benzyl esters being considerably less effective. Fluorescein mercuric acetate titration studies of inactivated yeast alcohol dehydrogenase and studies of the oxidized (disulfide) form of yeast glutathione reductase were consistent with inactivation processes involving sulfhydryl modification. Protection against nicotinoylacrylate inactivation was afforded by the binding of ligands to either the coenzyme or substrate binding sites. Inactivation of yeast alcohol dehydrogenase by ethyl nicotinoylacrylate exhibited an unexpected greater selectivity, resulting in the covalent modification of only one of the two reactive sulfhydryl groups at the catalytic site.