Proenkephalin (PENK)

Preproenkephalin has 267 amino acids, as does proopiomelanocortin. Both genes contain 2 introns. In both, all the repeated enkephalin or melanotropin sequences are encoded by a single large exon (exon 3). Preproenkephalin mRNA encodes 4 copies of met-enkephalin, 2 copies of met-enkephalin extended sequences, and 1 copy of leu-enkephalin. Each copy is flanked by paired basic amino acids which are presumably recognized by the processing protease.

The corresponding amino acid sequence shows that the precursor is 267 amino acids long and contains 6 interspersed Met-enkephalin sequences and 1 Leu-enkephalin sequence. The precursor does not contain the sequences of dynorphin, alpha-neo-endorphin or beta-endorphin.