Class III Alcohol Dehydrogenases: Evidence for Their Identity with the Glutathione-Dependent Formaldehyde Dehydrogenases

Alcohol dehydrogenases (EC 1.1.1.1) from human (Vallee and Bazzone, 1983), rat (Julia et al., 1987b), mouse (Algar et al., 1983) and other mammalian species (Julia et al., 1987a) are divided into three classes, I, H and III, which are characterized by their specific, differing electrophoretic mobilities, reactivities with different alcohols and sensitivities to pyrazole and its derivatives. Class III alcohol dehydrogenases have anodic electrophoretic mobility at neutral to alkaline pH, and they are further distinguished by their insensitivity to pyrazole and poor use of ethanol and other short-chain alcohols as substrate. Long-chain alcohols like 1-octanol are, in contrast, used well as substrates by these enzymes (Vallee and Bazzone, 1983). The class III alcohol dehydrogenases occur in mammalian tissues much more widely than the enzymes from the other classes (Julia et al., 1987b). The class III enzymes have been purified from human liver (Wagner et al., 1984) and brain (Beisswenger et al., 1985), and from the livers of horse (Kaiser et al., 1989), rat (Julia et al., 1987b) and mouse (Algar et al., 1983) but the physiological significance of these enzymes has remained obscure although their involvement in the oxidation of long-chain fatty alcohols or ω-hydroxy fatty acids has been postulated (Giri et al., 1989).