Characterization of the porcine carboxypeptidase E cDNA: comparative analysis and investigation of a non-synonymous SNP.

Carboxypeptidase E (CPE) is an important enzyme responsible for the proteolytic processing of prohormone intermediates. A naturally occurring point mutation, leading to an accumulation of many neuroendocrine peptides has been characterized within exon 5 of the CPE gene in mice. In the present study the sequence of the cDNA for the porcine CPE gene including all the coding region and the 3'-UTR region was generated. Comparisons with bovine, human, mouse, and rat CPE cDNA sequences showed that the coding regions of the gene are highly conserved both at the nucleotide and at the amino acid level. A very low nonsynonymous/synonymous substitution ratios between the proteins was found indicating that purifying selection is acting on the CPE gene. A nonsynonymous SNP identified at position 1272 in the transcript resulting in a codon change from TCA (Serine) to TTA (Leucine) was genotyped in the Danish pig populations. However, the mutated allele was only identified in one particular family. Exon 5 was sequenced in 45 unrelated pigs. No evidence of variation was found in this region. In accordance with previous results and in accordance with comparative mapping information the gene was accurately mapped to porcine chromosome 8 using the ImpRH panel.