Recommended nomenclature for the vertebrate alcohol dehydrogenase gene family

The alcohol dehydrogenase (ADH) gene family encodes enzymes that metabolize a wide variety of substrates, including ethanol, retinol, other aliphatic alcohols, hydroxysteroids, and lipid peroxidation products. Studies on 19 vertebrate animals have identified ADH orthologs across several species, and this has now led to questions of how best to name ADH proteins and genes. Seven distinct classes of vertebrate ADH encoded by non-orthologous genes have been defined based upon sequence homology as well as unique catalytic properties or gene expression patterns. Each class of vertebrate ADH shares <70% sequence identity with other classes of ADH in the same species. Classes may be further divided into multiple closely related isoenzymes sharing >80% sequence identity such as the case for class I ADH where humans have three class I ADH genes, horses have two, and mice have only one. Presented here is a nomenclature that uses the widely accepted vertebrate ADH class system as its basis. It follows the guidelines of human and mouse gene nomenclature committees, which recommend coordinating names across species boundaries and eliminating Roman numerals and Greek symbols. We recommend that enzyme subunits be referred to by the symbol "ADH" (alcohol dehydrogenase) followed by an Arabic number denoting the class; i.e. ADH1 for class I ADH. For genes we recommend the italicized root symbol "ADH" for human and "Adh" for mouse, followed by the appropriate Arabic number for the class; i.e. ADH1 or Adh1 for class I ADH genes. For organisms where multiple species-specific isoenzymes exist within a class, we recommend adding a capital letter after the Arabic number; i.e. ADH1A, ADH1B, and ADH1C for human alpha, beta, and gamma class I ADHs, respectively. This nomenclature will accommodate newly discovered members of the vertebrate ADH family, and will facilitate functional and evolutionary studies.