Class I and class IV alcohol dehydrogenase (retinol dehydrogenase) gene expression in mouse embryos.

Abstract

Mammalian alcohol dehydrogenase (ADH) exists as several classes of related enzymes, all linked evolutionarily to the medium-chain ADHs present in bacteria, fungi, plants, and animals (Kaiser et al., 1993). One distinctive feature of the mammalian ADH family is the ability of some members to act as retinol dehydrogenases as well as ethanol dehydrogenases (Zachman and Olson, 1961; Mezey and Holt, 1971; Boleda et al., 1993). ADH classes I and IV have been demonstrated to function in this manner in both humans and rodents (Yang et al., 1993; Boleda et al., 1993). This feature may be important since it implies that these classes of ADH may participate in the conversion of retinol (vitamin A alcohol) to its active forms including retinal and retinoic acid, the latter functioning as a transcriptional regulatory ligand controlling cellular differentiation (De Luca, 1991). It further implies that excessive ethanol consumption may competitively inhibit retinol oxidation by ADH, thus leading to under-utilization of vitamin A. This point is particularly critical when one considers a potential connection between vitamin A utilization by developing embryos and fetal alcohol syndrome, a form of teratogenesis characterized by ethanol-in-duced brain and craniofacial abnormalities (Duester, 1991).