:Hemorphin
{{Short description|Class of opioid peptides}}
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Hemorphins are a class of naturally occurring, endogenous opioid peptides which are found in the bloodstream, and are derived from the β-chain of hemoglobin.{{cite journal |vauthors=Brantl V, Gramsch C, Lottspeich F, Mertz R, Jaeger KH, Herz A | title = Novel opioid peptides derived from hemoglobin: hemorphins | journal = European Journal of Pharmacology | volume = 125 | issue = 2 | pages = 309–10 |date=June 1986 | pmid = 3743640 | doi = 10.1016/0014-2999(86)90044-0}}{{cite journal |vauthors=Davis TP, Gillespie TJ, Porreca F | title = Peptide fragments derived from the beta-chain of hemoglobin (hemorphins) are centrally active in vivo | journal = Peptides | volume = 10 | issue = 4 | pages = 747–51 | year = 1989 | pmid = 2587417 | doi = 10.1016/0196-9781(89)90107-1| s2cid = 11168006 }} They have antinociceptive effects via activation of the opioid receptors,{{cite journal |vauthors=Liebmann C, Schrader U, Brantl V | title = Opioid receptor affinities of the blood-derived tetrapeptides hemorphin and cytochrophin | journal = European Journal of Pharmacology | volume = 166 | issue = 3 | pages = 523–6 |date=August 1989 | pmid = 2553436 | doi = 10.1016/0014-2999(89)90368-3}} and some may also play a role in blood pressure through inhibition of the angiotensin-converting enzyme (ACE),{{cite journal |vauthors=Lantz I, Glämsta EL, Talbäck L, Nyberg F | title = Hemorphins derived from hemoglobin have an inhibitory action on angiotensin converting enzyme activity | journal = FEBS Letters | volume = 287 | issue = 1–2 | pages = 39–41 |date=August 1991 | pmid = 1652464 | doi = 10.1016/0014-5793(91)80011-Q| doi-access = free }} as well as cause an elevation of endogenous enkephalin levels.{{cite journal |vauthors=Benuck M, Berg MJ, Marks N | title = Separate metabolic pathways for Leu-enkephalin and Met-enkephalin-Arg(6)-Phe(7) degradation by rat striatal synaptosomal membranes | journal = Neurochemistry International | volume = 4 | issue = 5 | pages = 389–96 | year = 1982 | pmid = 20487892 | doi = 10.1016/0197-0186(82)90081-X| s2cid = 23138078 }} Some examples of hemorphins include hemorphin-4, spinorphin, and valorphin.