Enkephalin, pre-pro (ppENK)

Met-enkephalin (tyr-gly-gly-phe-met) and leu-enkephalin (tyr-gly-gly-phe-leu) are pentapeptides which compete with and mimic the effects of opiate drugs. Although interest in enkephalins stems largely from their possible role in the brain, the richest source of these peptides is the adrenal gland. The 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. (Because of structural similarities it had been postulated that beta-endorphin is precursor of Met-enkephalin, and that dynorphin or alpha-neo-endorphin is precursor of Leu-enkephalin.)  It is involved in the modulation of nociceptive pain. ppENK may be capable of enhancing immune function in cancer or AIDS patients.