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IUPAC name
60617-12-1 YesY
ChemSpider 28184601
Jmol interactive 3D Image
PubChem 16132316
Molar mass 3,465.03 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

β-Endorphin is an endogenous opioid neuropeptide found in the neurons of both the central and peripheral nervous system. It is one of five endorphins found in humans, the others of which include α-endorphin, γ-endorphin, α-neoendorphin, and β-neoendorphin.

The amino acid sequence is: Tyr-Gly-Gly-Phe-Met-Thr-Ser-Glu-Lys-Ser-Gln-Thr-Pro-Leu-Val-Thr-Leu-Phe-Lys-Asn-Ala-Ile-Ile-Lys-Asn-Ala-Tyr-Lys-Lys-Gly-Glu[1] (31 amino acids). The first 16 amino acids are identical to α-Endorphin.


β-Endorphin is a peptide, 31 amino acids long, resulting from processing of the precursor proopiomelanocortin (POMC). (Note, POMC also gives rise to other peptide hormones, including adrenocorticotropic hormone (ACTH), as well α- and γ-melanocyte-stimulating hormone (MSH), resulting from intracellular processing by internal enzymes known as prohormone convertases.)

β-Endorphin is found in neurons of the hypothalamus, as well as the pituitary gland.


It is an agonist of the opioid receptors, with evidence suggesting it serves as the endogenous ligand of the μ-opioid receptor, the same receptor to which the chemicals extracted from opium, such as morphine, have their analgesic (indeed, the μ-opioid receptor was named based on its most renowned ligand, morphine).


β-Endorphin was discovered in camel pituitary extracts by C.H. Li and David Chung.[2]


It is used as an analgesic in the body to numb or dull pains. That is the reason why humans start to feel better immediately after an acute physical trauma even though the symptoms are still present. The reason the pain dulls is because it binds to and activates opioid receptors. β-Endorphin has approximately 18 to 33 times the analgesic potency of morphine,[3] though its hormonal effect is species dependent.[4]


β-Endorphin release in response to exercise has been known and studied since at least the 1980s.[5] Studies have demonstrated that serum concentrations of endogenous opioids, in particular β-endorphin and β-lipotrophin, increase in response to both acute exercise and training.[5] The notion of β-endorphin release during exercise is colloquially known in popular culture as a runner's high.[6]


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