Alcohol dehydrogenase (<db_xref db="EC" dbkey="1.1.1.1"/>) (ADH) catalyzes the reversible oxidation ofalcohols to their corresponding acetaldehyde or ketone with the concomitant reduction of NAD:<reaction>alcohol + NAD = aldehyde or ketone + NADH</reaction>Currently three structurally and catalytically different types of alcoholdehydrogenases are known:<ol><li>Zinc-containing 'long-chain' alcohol dehydrogenases.</li><li>Insect-type, or 'short-chain' alcohol dehydrogenases.</li><li>Iron-containing alcohol dehydrogenases.</li></ol>Zinc-containing ADH's [<cite idref="PUB00001354"/>, <cite idref="PUB00003420"/>] are dimeric or tetrameric enzymes that bind twoatoms of zinc per subunit. One of the zinc atom is essential for catalyticactivity while the other is not. Both zinc atoms are coordinated by eithercysteine or histidine residues; the catalytic zinc is coordinated by twocysteines and one histidine. Zinc-containing ADH's are found in bacteria,mammals, plants, and in fungi. In many species there is more than one isozyme(for example, humans have at least six isozymes, yeast have three, etc.). Anumber of other zinc-dependent dehydrogenases are closely related to zincADH [<cite idref="PUB00001658"/>] and are included in this family.<ul><li>Sorbitol dehydrogenase (<db_xref db="EC" dbkey="1.1.1.14"/>)</li><li>L-threonine 3-dehydrogenase (<db_xref db="EC" dbkey="1.1.1.103"/>)</li><li>Glutathione-dependent formaldehyde dehydrogenase (<db_xref db="EC" dbkey="1.1.1.284"/>)</li><li>Mannitol dehydrogenase (<db_xref db="EC" dbkey="1.1.1.255"/>)</li></ul><p> In addition, this family includes NADP-dependent quinone oxidoreductase (<db_xref db="EC" dbkey="1.6.5.5"/>),an enzyme found in bacteria (gene qor), in yeast and in mammals where, in somespecies such as rodents, it has been recruited as an eye lens protein and isknown as zeta-crystallin [<cite idref="PUB00001655"/>]. The sequence of quinone oxidoreductase isdistantly related to that other zinc-containing alcohol dehydrogenases and itlacks the zinc-ligand residues. The torpedo fish and mammalian synaptic vesiclemembrane protein vat-1 is related to qor.</p><p>This entry represents the cofactor-binding domain of these enzymes, which is normally found towards the C terminus. Structural studies indicate that it forms a classical Rossman fold that reversibly binds NAD(H) [<cite idref="PUB00022446"/>, <cite idref="PUB00027598"/>, <cite idref="PUB00028130"/>].</p> Alcohol dehydrogenase, C-terminal