Alcohol dehydrogenase. Exhibits high activity for ethanol oxidation and plays a major role in ethanol catabolism. a primary alcohol + NAD(+) = an aldehyde + H(+) + NADH ethanol + NAD(+) = acetaldehyde + H(+) + NADH Binds 2 Zn(2+) ions per subunit. Dimer of identical or non-identical chains of class I alcohol dehydrogenase: ADH1A, ADH1B, and ADH1C. Expressed in kidney. There are 7 different ADH's isozymes in human: three belongs to class-I: ADH1A, ADH1B, and ADH1C, one to class-II: ADH4, one to class-III: ADH5, one to class-IV: ADH7 and one to class-V: ADH6. Belongs to the zinc-containing alcohol dehydrogenase family.