encefalinas

Enkephalins, also known in Spanish as encefalinas, are endogenous opioid peptides that function as neurotransmitters and neuromodulators in the vertebrate nervous system. The two main enkephalins are met-enkephalin and leu-enkephalin, both pentapeptides with the sequences Tyr-Gly-Gly-Phe-Met and Tyr-Gly-Gly-Phe-Leu, respectively. They are derived from the larger precursor protein proenkephalin.

Biogenesis and distribution: Enkephalins are produced from the PENK gene and processed by proteolytic enzymes to yield the active peptides. They are found in many brain regions involved in pain processing, including the striatum, nucleus accumbens, periaqueductal gray, dorsal horn of the spinal cord, amygdala, and hypothalamus, as well as in peripheral tissues such as the adrenal medulla and the gastrointestinal tract.

Function and mechanism: Enkephalins interact primarily with μ- and δ-opioid receptors. Their activation inhibits neurotransmitter release by triggering intracellular signaling that reduces neuronal excitability, contributing to endogenous analgesia. They also influence mood, stress responses, and autonomic regulation.

Metabolism and research context: Enkephalins are rapidly degraded by peptidases, notably enkephalinases such as neutral endopeptidase and aminopeptidase N, which shortens their activity. Research into enkephalin analogs and enzyme inhibitors has explored potential analgesic applications, though clinical use is limited by issues of stability and tolerance.