Cloning and expression of the bovine 11beta-hydroxysteroid dehydrogenase type-2.

The bovine 11beta-hydroxysteroid dehydrogenase type 2 enzyme (11beta-HSD-2) cDNA was cloned from three overlapping PCR fragments using primers based on the human and ovine 11beta-HSD-2 cDNA sequences. Both cDNA ends were obtained by a modified RACE (Rapid Amplification of cDNA Ends) method. The bovine 11beta-HSD-2 cDNA is 1878 bp long, excluding the poly(A) tail. It consists of a 5'-untranslated region of 133 bp, an open reading frame of 1215 bp and a 3'-untranslated region of 530 bp. Bovine 11beta-HSD-2 cDNA is highly homologous to that of the sheep (92%) and less related to the human (67%), rabbit (65%), rat (52%) and mouse (45%) cDNA. The predicted bovine 11beta-HSD-2 protein contains 404 amino acid residues with a calculated mol wt of 43,985. It is homologous to the sheep (98%) and human (88%) protein, and less related to that of the rabbit (76%), rat (80%) and mouse (77%). The cloned 11beta-HSD-2 cDNA was transfected into CHOP cells and the enzymatic characteristics determined. The enzyme functions primarily as an oxidase, uses NAD(+) and is more active with corticosterone as a substrate than with cortisol or dexamethasone. It is expressed in high concentrations in kidney, adrenal and colon, and in small concentrations in liver, heart and lung. In conclusion, the 11beta-HSD-2 enzyme of cattle is very similar to that of other species in its structure and enzymatic characteristics.