Cytosolic and mitochondrial isozymes of horse liver aldehyde dehydrogenase

Two isozymes of horse liver aldehyde dehydrogenase, Fl and F2, have been purified to homogeneity using salt fractionation followed by ion exchange and gel filtration chromatography. The two isozymes are similar in several respects: molecular weight (200-300 kD), subunit molecular weight (52-53 kD), amino acid composition, broad aldehyde specificity (aromatic and aliphatic), high specificity for NAD over NADP (K(m) NADP/K(m) NAD 300), sensitivity to pCMB and chloral hydrate inhibition, and p nitrophenyl esterase activity. On the other hand, significant differences between these two isozymes have been observed: K's for aldehydes and NAD, sensitivity to disulfiram, and subcellar localization. On the basis of its very low K for NAD, its reasonably low K for acetaldehyde, and its high sensitivity to disulfiram, it is suggested that the Fl isozyme may play a major role in the metabolism of acetaldehyde produced during ethanol oxidation in vivo.