We describe the cloning and sequencing of porcine 17 beta-estradiol dehydrogenase. The enzyme performs oxidation 360-fold more efficiently than reduction, both measured under optimal conditions. It is localized in specialized vesicles of epithelial cells. The cDNA clones were isolated from a lambda UNI ZAP XR library of porcine kidney and polymerase-chain-reaction-amplified from templates of uterus epithelium. In both tissues, the same enzyme is coded by a transcript of 2.9 kb. It contains a 69-b 5'-noncoding region, an open reading frame of 2211 b and a 3'-noncoding region of 624 b. The open reading frame of 737 amino acids with a predicted molecular mass 79,973 Da was confirmed by amino acid sequencing of peptides. The 80-kDa translation product is processed to the N-terminal 32-kDa enzyme, part of which is then covalently linked to actin. The estradiol dehydrogenase/actin complex and the 80-kDa translation product comigrate in SDS/PAGE.