Editing Endorphins (section)

== Synthesis ==
Endorphin precursors are primarily produced in the [[pituitary gland]].<ref>{{cite journal | vauthors = Burbach JP | title = Action of proteolytic enzymes on lipotropins and endorphins: biosynthesis, biotransformation and fate | journal = Pharmacology & Therapeutics | volume = 24 | issue = 3 | pages = 321–354 | date = January 1984 | pmid = 6087385 | doi = 10.1016/0163-7258(84)90008-1 | hdl-access = free | hdl = 1874/25178 }}</ref><ref name=":42">{{cite journal | vauthors = Mousa SA, Shakibaei M, Sitte N, Schäfer M, Stein C | title = Subcellular pathways of beta-endorphin synthesis, processing, and release from immunocytes in inflammatory pain | journal = Endocrinology | volume = 145 | issue = 3 | pages = 1331–1341 | date = March 2004 | pmid = 14630714 | doi = 10.1210/en.2003-1287 | doi-access = free }}</ref><ref>{{cite journal | vauthors = Takahashi A, Mizusawa K | title = Posttranslational modifications of proopiomelanocortin in vertebrates and their biological significance | journal = Frontiers in Endocrinology | volume = 4 | pages = 143 | date = October 2013 | pmid = 24146662 | pmc = 3797980 | doi = 10.3389/fendo.2013.00143 | doi-access = free }}</ref> All three types of endorphins are fragments of the precursor protein [[proopiomelanocortin]] (POMC). At the [[trans-Golgi network]], POMC binds to a membrane-bound protein, [[carboxypeptidase E]] (CPE).<ref name=":432">{{cite journal | vauthors = Mousa SA, Shakibaei M, Sitte N, Schäfer M, Stein C | title = Subcellular pathways of beta-endorphin synthesis, processing, and release from immunocytes in inflammatory pain | journal = Endocrinology | volume = 145 | issue = 3 | pages = 1331–1341 | date = March 2004 | pmid = 14630714 | doi = 10.1210/en.2003-1287 | doi-access = free }}</ref> CPE facilitates POMC transport into immature budding vesicles.<ref>{{cite journal | vauthors = Loh YP, Kim T, Rodriguez YM, Cawley NX | title = Secretory granule biogenesis and neuropeptide sorting to the regulated secretory pathway in neuroendocrine cells | journal = Journal of Molecular Neuroscience | volume = 22 | issue = 1–2 | pages = 63–71 | date = 2004 | pmid = 14742911 | doi = 10.1385/jmn:22:1-2:63 }}</ref> In mammals, pro-peptide convertase 1 (PC1) cleaves POMC into [[adrenocorticotropin]] (ACTH) and [[beta-lipotropin]] (β-LPH).<ref name=":432" /> β-LPH, a pituitary hormone with little opiate activity, is then continually fragmented into different peptides, including α-endorphin, β-endorphin, and γ-endorphin.<ref name=":1">{{cite journal | vauthors = Ambinder RF, Schuster MM | title = Endorphins: new gut peptides with a familiar face | journal = Gastroenterology | volume = 77 | issue = 5 | pages = 1132–1140 | date = November 1979 | pmid = 226450 | doi = 10.1016/S0016-5085(79)80089-X | doi-access = free }}</ref><ref name=":2">{{cite journal | vauthors = Crine P, Gianoulakis C, Seidah NG, Gossard F, Pezalla PD, Lis M, Chrétien M | title = Biosynthesis of beta-endorphin from beta-lipotropin and a larger molecular weight precursor in rat pars intermedia | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 75 | issue = 10 | pages = 4719–4723 | date = October 1978 | pmid = 216997 | pmc = 336191 | doi = 10.1073/pnas.75.10.4719 | doi-access = free | bibcode = 1978PNAS...75.4719C }}</ref><ref name=":3">{{cite journal | vauthors = Goldstein A | title = Opioid peptides endorphins in pituitary and brain | journal = Science | volume = 193 | issue = 4258 | pages = 1081–1086 | date = September 1976 | pmid = 959823 | doi = 10.1126/science.959823 | bibcode = 1976Sci...193.1081G }}</ref> Peptide convertase 2 (PC2) is responsible for cleaving β-LPH into β-endorphin and γ-lipotropin.<ref name="Purves2018" /> Formation of α-endorphin and γ-endorphin results from proteolytic cleavage of β-endorphin.<ref name=":562"/>