title: Isolation and structure of a novel C-terminally amidated opioid peptide, amidorphin, from bovine adrenal medulla.
abstract: Biologically active peptide hormones and neurotransmitters have been shown to be enzymatically liberated from larger, inactive precursor molecules by tissue-specific post-translational processing, particularly at the typical cleavage signals of paired basic residues. Subsequent N-terminal or C-terminal modifications may be of importance in regulating the biological activities of these peptides. C-terminal alpha-amidation is considered to be essential for the biological function of several non-opioid peptides. Here we present the isolation and structure of a novel C-terminally amidated opioid peptide, amidorphin, from bovine adrenal medulla. Amidorphin and the recently isolated octapeptide metorphamide (adrenorphin) are the only endogenous opioid peptides in mammals known to possess a C-terminal amide group. The amino acid sequence of amidorphin corresponds to the sequence 104-129 of bovine proenkephalin A. Very high concentrations of amidorphin were detected in bovine adrenal medulla and in a further endocrinological system, the hypothalamic-neurohypophyseal axis. Amidorphin may therefore be considered to be a major gene product of the opioid peptide precursor proenkephalin A in these endocrine tissues.
mesh_terms: D000313:Adrenal Medulla / Q000032:analysis*; D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D004723:Endorphins / Q000302:isolation & purification*; D007030:Hypothalamo-Hypophyseal System / Q000032:analysis
chemical_list: D004723:Endorphins