The mammalian alcohol dehydrogenase genome shows several gene duplications and gene losses resulting in a large set of different enzymes including pseudoenzymes

Mammalian alcohol dehydrogenase (ADH) is a protein family divided into six classes and the number of known family members is increasing rapidly. Several primate genomes are completely analyzed for the ADH region, where higher primates (human and hominoids) have seven genes of classes ADH1–ADH5. Within the group of non-hominoids apes there have been further duplications and species with more than the typical three isozymic forms for ADH1 are present. In contrast there are few completely analyzed ADH genomes in the non-primate group of mammals, where an additional class has been identified, ADH6, that has been lost during the evolution of primates. In this study 85 mammalian genomes with at least one ADH gene have been compiled. In total more than 500 ADH amino acid sequences were analyzed for patterns that distinguish the different classes.For ADH1–ADH4 intensive investigations have been performed both at the functional and at structural levels. However, a corresponding functional protein to the ADH5 gene, which is found in most ADH genomes, has never been detected. The same is true for ADH6, which is only present in non-primates.The entire mammalian ADH family shows a broad spectrum of gene duplications and gene losses where the numbers differ from six genes (most non-primate mammals) up to ten genes (vole). Included in these sets are examples of pseudogenes and pseudoenzymes.