The role of cytoplasmic aldehyde dehydrogenase in the metabolism of N-tele-methylhistamine.

The subcellular distributions of aldehyde dehydrogenase activities towards acetaldehyde have been compared with those toward N-tele-methylimidazole acetaldehyde, the aldehyde derived from the oxidation of N-tele-methylhistamine. At high concentrations of acetaldehyde (3.0 mM), significant aldehyde dehydrogenase activity can be found in the mitochondrial, light mitochondrial, microsomal and cytoplasmic fractions whereas, when the activity is determined with 15 microM acetaldehyde, the enzyme activity is enriched only in the mitochondrial fraction suggesting that this organelle will be the dominant site for the metabolism of acetaldehyde derived from ingested ethanol. The activity towards N-tele-methylimidazole acetaldehyde was determined by generating this compound in the assay by the oxidation of N-tele-methylhistamine in the presence of beef plasma amine oxidase. At the low steady-state aldehyde concentrations that will be present in such an assay, only the cytoplasmic form of aldehyde dehydrogenase showed activity towards this substrate.