Mouse aldehyde dehydrogenase genetics: positioning of Ahd-1 on chromosome 4

Liver cytosolic aldehyde dehydrogenases from "alcohol-drinking" and "alcohol-avoiding" mouse strains: purification and molecular properties

Liver cytosolic aldehyde dehydrogenases (AHD-2) have been isolated in a highly purified state from "alcohol-drinking" (C57BL/6J) and "alcohol-avoiding" (DBA/2J) strains of mice. The purified enzymes were resolved into three major and one minor form of activity by isoelectric focusing (IEF) techniques and showed similar zymogram patterns. The enzymes had identical subunit sizes on SDS-polyacrylamide gels: 53,000. Gel exclusion chromatography, using Ultrogel AcA34, indicated that the enzymes were dimers. The enzymes exhibited biphasic kinetic characteristics and were readily distinguished from each other. The purified forms of AHD-2 from C57BL/6J and DBA/2J mice exhibited two apparent Km values in each case: 10 microM/100 microM and 30 microM/330 microM respectively. AHD-2 exhibited a broad pH optimum in the range 7.0-9.0 and was very sensitive towards disulphuram inhibition, with 50% inhibition occurring at 0.17 microM. The kinetic results support proposals that AHD-2 may be the primary enzyme for oxidizing acetaldehyde during ethanol oxidation in vivo.

Mouse mitochondrial aldehyde dehydrogenase isozymes: purification and molecular properties

Aldehyde dehydrogenase isozymes (AHD-1 and AHD-5) have been isolated in a highly purified state from extracts of mouse liver mitochondria. The enzymes have distinct subunit sizes, as determined by SDS/polyacrylamide gel electrophoresis: AHD-1, 63,000; AHD-5, 49,000. Gel exclusion chromatography, using sephadex G-200, indicated that both isozymes are dimers, although AHD-1 may also exist as a monomeric form as well. The enzymes exhibited widely divergent kinetic characteristics. The purified allelic forms of AHD-1, AHD-1A (C57BL/6J mice) and AHD-1B (CBA/H mice), exhibited high Km values with acetaldehyde as substrate, 1.4 mM and 0.78 mM respectively, whereas AHD-5 exhibited a low Km value with acetaldehyde of 0.2 microM. In addition, the isozymes exhibited distinct pH optima for catalysis (AHD-1, pH range 6.5-7.5; AHD-5, pH range 8.5-10.0), and were differentially sensitive towards disulphuram inhibition, with 50% inhibition occurring 13 and 0.1 microM for the AHD-1 and AHD-5 isozyme respectively. Based upon the kinetic characteristics, it is suggested that AHD-5 may be the primary enzyme for oxidizing mitochondrial acetaldehyde during ethanol oxidation in vivo.