ALDEHYDE DEHYDROGENASE (EC 1.2.1.3) - COMPARISON OF SUBCELLULAR-LOCALIZATION OF THE 3RD ISOZYME THAT DEHYDROGENATES GAMMA-AMINOBUTYRALDEHYDE IN RAT, GUINEA-PIG AND HUMAN LIVER

1. Subcellular fractionation of rat, guinea pig and human livers showed that aldehyde dehydrogenase metabolizing gamma-aminobutyraldehyde was exclusively localized in the cytoplasmic fraction in all three mammalian species. 2. Total gamma-aminobutyraldehyde activity of aldehyde dehydrogenase was found to be ca 0.41, 0.3 and 0.24-mu-mol NADH min-1 g-1 tissue, respectively in rat, guinea pig and human liver, with more than 95% of activity in the cytoplasm. 3. Partially purified cytoplasmic isozyme from rat liver showed similar chromatographic behavior and kinetic properties to the E3 isozyme isolated from human liver. 4. The rat isozyme was insensitive to disulfiram (40-mu-M) and to magnesium (160-mu-M) and had K(m) values of 5-mu-M (pH 7.4) for gamma-aminobutyraldehyde, 7.5-mu-M (pH 9.0) for propionaldehyde and 4-mu-M (pH 7.4) for NAD.