CDNA cloning and physical mapping of porcine 3 beta-hydroxysteroid dehydrogenase/Delta 5-Delta 4 isomerase

The 3 beta -hydroxvsteroid dehydrogenase/Delta5-Delta4-isomerase (3 beta -H SD) enzymes are essential for the biosynthesis of steroid hormones. The 3 b eta -HSD gene family has been reported to encode for different isoenzymes w hich function either as dehydrogenase/isomerase or as reductase. The 3 beta -HSD enzymes are involved in the formation of the pheromone androstenone ( 5 alpha -androst-16-ene-3-one) which contributes to the unpleasant odour pr esent in the meat of uncastrated boars. An reverse-transcription-polymerase chain reaction (RT-PCR) probe from porcine testicular tissue of a 3 beta - HSD enzyme was used to screen a porcine adipose tissue cDNA library. Both s trands of the positive clones were sequenced and the putative coding sequen ce of 1122 nucleotides encodes 374 amino acids. Comparison of the putative open reading frame with the bovine and the human type I homologues revealed 85.6 and 79.3% identity, respectively. Fluorescence in situ hybridization (FISH) was performed with a labelled PAC clone containing the gene of inter est. The 3 beta -HSD gene was mapped to the porcine chromosome 4q16-4q21 wh ich is in accordance with the comparative gene map.