What is "met-enkephalin"

alt. (context biochemistry English) One of a pair of pentapeptides, (Tyr-Gly-Gly-Phe-Met) occurring naturally in the brain, that affects pain perception. n. (context biochemistry English) One of a pair of pentapeptides, (Tyr-Gly-Gly-Phe-Met) occurring naturally in the brain, that affects pain perception.

Met-enkephalin, also known as metenkefalin ( INN), sometimes referred to as opioid growth factor (OGF), is a naturally occurring, endogenous opioid peptide that has opioid effects of a relatively short duration. It is one of the two forms of enkephalin, the other being leu-enkephalin. The enkephalins are considered to be the primary endogenous ligands of the δ-opioid receptor, due to their high potency and selectivity for the site over the other endogenous opioids.