Enkephalin

Enkephalin" refers to a family of endogenous opioid pentapeptides primarily involved in modulating nociception (pain perception), stress responses, and other neurophysiological processes[9][10][3][1]. There are two main forms: **methionine-enkephalin** (Met-enkephalin) and **leucine-enkephalin** (Leu-enkephalin), both produced by cleavage of the proenkephalin precursor[3][6][7]. Enkephalins function as neurotransmitters and neuromodulators in the CNS and are major endogenous ligands for the delta-opioid receptor, with some activity at the mu-opioid receptor[1][4][5]. The term "Enkephalin pathway" is imprecise, as molecules or receptors—not functional pathways—are considered drug targets; more precise targets would be "delta-opioid receptor," "mu-opioid receptor," or "Opioid growth factor receptor." Enkephalins also play roles in stress adaptation, immune regulation, and cell proliferation. Dysregulation of enkephalin signaling is implicated in pain disorders, addiction, some cancers, neurodegenerative and inflammatory diseases[5][8][1]. Enkephalin levels can be potential biomarkers for certain pain conditions, and modulating their degradation (e.g., via enkephalinase inhibitors) is a therapeutic strategy under investigation. **Notes regarding this entry:** - "Enkephalin pathway" does **not** refer to a specific molecule or receptor, but rather to a functional axis or signaling network involving enkephalin peptides and their receptors. Thus, it is not a canonical therapeutic target by the criteria given—is_incorrect: true[1][3][9]. - To map to targets in drug discovery databases, use the terms "Delta-opioid receptor," "Mu-opioid receptor," or "Opioid growth factor receptor" as specific, actionable targets. Enkephalin itself is a ligand, not a receptor or drug target.

Other names

EnkephalinsMet-enkephalinLeu-enkephalinOpioid growth factor (OGF)MENKMet-enkMethionine-enkephalinLeucine-enkephalin

Activation of delta-opioid receptor and mu-opioid receptor (agonist activity); Upregulation of cell cycle inhibitors (via OGF-OGFr axis)