Opioid Peptide Family

Four major genes are associated with opioid peptide production: proenkephalin (PENK), prodynorphin (PDYN), pronociceptin/orphanin FQ (PNOC), and proopiomelanocortin (POMC). Each gene codes for one or more opioid peptides. In humans, six Met-enkephalin sequences and one Leu-enkephalin sequence are encoded by PENK, three dynorphin-related sequences are encoded by PDYN, three nociceptin/orphanin FQ-related sequences are encoded by PNOC, and the beta-endorphin sequence is encoded by POMC. These genes are expressed in the nervous system, including the brain and peripheral tissues, where several opioid peptides are generated from precursor proteins and/or gene products. Generated peptides are associated with pain perception, analgesia, and other physiological functions mediated by a group of opioid receptors.