Aldehyde Dehydrogenases in Rat Liver

Abstract

Two enzymes (I and II) with NAD + -dependent aldehyde dehydrogenase activity have been separated and partially purified from the supernatant fraction of rat liver. Resolution was effected by DEAE-cellulose column chromatography. In addition to the differences in charge properties, these two proteins differ in substrate specificity, that of enzyme II being comparatively restricted. Enzyme I has a relatively sharp optimum in activity at pH 8 whereas enzyme II exhibits an optimal range between pH 8 and 9.5. Both enzymes are strongly inhibited by low concentrations of p-chloromercuribenzene sulfonic acid and this inhibition can be reversed by dithiothreitol. Both enzymes are also inhibited by arsenite; inhibition of enzyme I is enhanced by mercaptoethanol but inhibition of enzyme II is not so affected. Molecular weight estimation by gel filtration indicates each protein has a molecular weight of approximately 180 000.