a primary alcohol + NAD(+) = an aldehyde + H(+) + NADH a secondary alcohol + NAD(+) = a ketone + H(+) + NADH Binds 2 Zn(2+) ions per subunit. Dimer of identical or non-identical chains of three types (A, B, C), which are coded by 3 separate genes at different loci. Expressed at high levels in the liver, small intestine and eye, at moderate levels in kidney, ovary and uterus, and at low levels in the spinal cord, thymus, heart, stomach mucosa, skin and testis. Belongs to the zinc-containing alcohol dehydrogenase family. Class-I subfamily.