Abstract
The subcellular distribution of aldehyde reductase activity has been studied in chicken liver. Most of the activity with D-erythrose as a substrate appeared in cytosol, but 11% of the total activity appeared to be present in mitochondria. Two reduced nicotinamide adenine dinucleotide phosphate (NADPH)-dependent aldehyde reductases from chicken liver mitochondria have been partially purified and characterized. One enzyme (mitochondrial aldehyde reductase I) has a molecular weight of 29000 and has an isoelectric point of 7.0, whereas a second enzyme (mitochondrial aldehyde reductase II) has a molecular weight of 31000 and has an isoelectric point of 7.7. Substrate specificity studies showed that mitochondrial aldehyde reductase 1 and II are capable of reducing various aldehydes such as D-glyceraldehyde, D-erythrose, D-erythrose 4-phosphate and aromatic aldehydes. Unlike mitochondrial aldehyde reductase II, mitochondrial aldehyde reductase 1 very efficiently reduces D-glucuronic acid and succinic semialdehyde, and has higher Km values for aldehydes. Mitochondrial aldehyde reductase I activity is much more susceptible to inhibition by sodium valproate than mitochondrial aldehyde reductase II activity. With respect to substrate specificity and inhibitor sensitivity, mitochondrial aldehyde reductase I and II could be classified as high-Km aldehyde reductase and low-Km aldehyde reductase, respectively.
