Nomenclature of alcohol dehydrogenases.

Six different classes of mammalian alcohol dehydrogenase have been characterized. Most, if not all, are common to humans, mammals and many vertebrates, which therefore share class distinctions in general. Amino acid residue identities between classes are at the 60% level (70% in the case of one pair, class I/IV), whereas those for mammalian species variants within a class are still more extensive. Isozymes, derived from the most recent level of gene duplications, have been reported for class I (in seven species) and class III (in one species) thus far. In humans, the system appears to account for at least eight genes (ADH1-8), with corresponding subunits. Nomenclature is reviewed and suggested for alcohol dehydrogenases in nature, for the human enzyme system and for the mammalian forms.