An NADP+-dependent alcohol dehydrogenase (allyl-ADH) was isolated from the cultured cells of Nicotiana tabacum. The allyl-ADH was found to be efficient for the dehydrogenation of secondary allylic alcohols rather than saturated secondary alcohols and it was specific for the S-stereoisomer of the alcohols. The enzyme catalyzed the reversible reaction whereby the carbonyl group of enones is reduced to the corresponding allylic alcohol or vice versa. Two possible primary structures of the allyl-ADH were deduced by the sequence analyses of full-length cDNAs (allyl-ADH1 and ally-ADH2), which were cloned by the PCR method. These analyses indicated that the allyl-ADHs are composed of 343 amino acids having the molecular weights 38083 and 37994, respectively, and they showed approximately 70% homology to the NADP+-dependent oxidoreductases belonging to a plant zeta-crystallin family.