/en kef"euh lin/ , n. Biochem.
either of two pentapeptides that bind to morphine receptors in the central nervous system and have opioid properties of relatively short duration; one pentapeptide (Met enkephalin) has the amino acid sequence Tyr-Gly-Gly-Phe-Met and the other (Leu enkephalin) has the sequence Tyr-Gly-Gly-Phe-Leu.
[ 1970-75; enképhal ( os ) ENCEPHALON + -IN 2 ]