Biochemical and genetic studies on mouse aldehyde dehydrogenases.

Aldehyde dehydrogenase (AHD) exists as isozymes which are differentially distributed among tissues and subcellular fractions of mouse tissues. Genetic variants for liver mitochondrial (AHD-1) and cytoplasmic (AHD-2) isozymes have been used to map the responsible loci (Ahd-1 and Ahd-2) on chromosomes 4 and 19 respectively. Evidence for a regulatory locus (Ahd-3r) controlling the inducibility of the mouse liver microsomal isozyme (AHD-3) has also been obtained. More recent studies have described genetic and biochemical evidence for three additional AHD isozymes: a stomach isozyme (AHD-4); another liver mitochondrial enzyme (AHD-5); and a testis isozyme (AHD-6). Genetic analyses have indicated that AHD-4 and AHD-6 are encoded by distinct but closely linked loci on the mouse genome (Ahd-4 and Ahd-6), which segregate independently of Ahd-1 and Ahd-2. Liver mitochondrial isozymes, AHD-1 and AHD-5, have been purified to homogeneity using affinity chromatography. The very high affinity of AHD-5 for acetaldehyde suggests that this enzyme is predominantly responsible for acetaldehyde oxidation in mouse liver mitochondria.