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Molar mass 2947.29 g/mol
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Amidorphin is an endogenous, C-terminally amidated, opioid peptide generated as a cleavage product of proenkephalin A in some mammalian species; in humans and most other species, the peptide is 1 residue longer and is not amidated. Amidorphin is widely distributed in the mammalian brain, with particularly high concentrations found in the striatum, and outside of the brain in adrenal medulla and posterior pituitary.[1][2] The 26-residue peptide named amidorphin is found in several species including bovine (Bos taurus), sheep (Ovis aries), and pig (Sus scrofa). Humans and commonly studied lab animals (mice, rats) produce a 27-residue peptide that does not have an amidated C-terminal residue; this is due to the absence of a Gly in the precursor sequence and replacement with Ala, which is not a substrate for the amidating enzyme (Peptidyl-glycine alpha-amidating monooxygenase). The properties of the 27-residue peptide are presumably similar to those of amidorphin, although this has not been adequately tested.

In some brain areas, amidorphin is extensively further reduced into smaller fragments, such as the non-opioid peptide amidorphin-(8-26), or in humans, amidorphin-8-27. Cleavage of amidorphin into these smaller fragments releases the N-terminal [Met]-enkephalin sequence of amidorphin.[3]

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  1. ^ Seizinger BR; Liebisch DC; Gramsch C; et al. (1985). "Isolation and structure of a novel C-terminally amidated opioid peptide, amidorphin, from bovine adrenal medulla". Nature. 313 (5997): 57–9. doi:10.1038/313057a0. PMID 3965972. S2CID 4363051.
  2. ^ Liebisch DC, Seizinger BR, Michael G, Herz A (November 1985). "Novel opioid peptide amidorphin: characterization and distribution of amidorphin-like immunoreactivity in bovine, ovine, and porcine brain, pituitary, and adrenal medulla". Journal of Neurochemistry. 45 (5): 1495–503. doi:10.1111/j.1471-4159.1985.tb07218.x. PMID 4045460.
  3. ^ Liebisch DC, Weber E, Kosicka B, Gramsch C, Herz A, Seizinger BR (March 1986). "Isolation and structure of a C-terminally amidated nonopioid peptide, amidorphin-(8-26), from bovine striatum: a major product of proenkephalin in brain but not in adrenal medulla". Proceedings of the National Academy of Sciences of the United States of America. 83 (6): 1936–40. doi:10.1073/pnas.83.6.1936. PMC 323199. PMID 3456613.