enkephalin, leucine Enkephalin, Leucine: One of the endogenous pentapeptides with morphine-like activity. It differs from MET-ENKEPHALIN in the LEUCINE at position 5. Its first four amino acid sequence is identical to the tetrapeptide sequence at the N-terminal of BETA-ENDORPHIN.. Leu-enkephalin : A pentapeptide comprising L-tyrosine, glycine, glycine, L-phenylalanine and L-leucine residues joined in sequence by peptide linkages. It is an endogenous opioid peptide produced in vertebrate species, including rodents, primates and humans that results from decomposition of proenkephalin or dynorphin and exhibits antinociceptive properties. | 1.96 | 1 | 0 | pentapeptide; peptide zwitterion | analgesic; delta-opioid receptor agonist; human metabolite; mu-opioid receptor agonist; neurotransmitter; rat metabolite |