Biology:Opioid peptide

From HandWiki
Short description: Class of peptides that bind to opioid receptors
Vertebrate endogenous opioids neuropeptide
Identifiers
SymbolOpiods_neuropep
PfamPF01160
InterProIPR006024
PROSITEPDOC00964
Structural correlation between met-enkephalin, an opioid peptide (left), and morphine, an opiate drug (right)

Opioid peptides or opiate peptides are peptides that bind to opioid receptors in the brain; opiates and opioids mimic the effect of these peptides. Such peptides may be produced by the body itself, for example endorphins. The effects of these peptides vary, but they all resemble those of opiates. Brain opioid peptide systems are known to play an important role in motivation, emotion, attachment behaviour, the response to stress and pain, control of food intake, and the rewarding effects of alcohol and nicotine.

Opioid-like peptides may also be absorbed from partially digested food (casomorphins, exorphins, and rubiscolins). Opioid peptides from food typically have lengths between 4–8 amino acids. Endogenous opioids are generally much longer.

Opioid peptides are released by post-translational proteolytic cleavage of precursor proteins. The precursors consist of the following components: a signal sequence that precedes a conserved region of about 50 residues; a variable-length region; and the sequence of the neuropeptides themselves. Sequence analysis reveals that the conserved N-terminal region of the precursors contains 6 cysteines, which are probably involved in disulfide bond formation. It is speculated that this region might be important for neuropeptide processing.[1]

Endogenous

The human genome contains several homologous genes that are known to code for endogenous opioid peptides.

While not peptides, codeine and morphine are also produced in the human body.[6][7]

Endogenous opioid peptides and their receptors
Opioid peptide Amino acid sequence Opioid receptor target(s) References
Enkephalins
Leu-enkephalin YGGFL δ-opioid receptor†, μ-opioid receptor† [8][9][10]
Met-enkephalin YGGFM δ-opioid receptor†, μ-opioid receptor† [8][9][10]
Metorphamide YGGFMRRV-NH2 δ-opioid receptor, μ-opioid receptor [8]
Peptide E YGGFMRRVGRPEWWMDYQKRYGGFL μ-opioid receptor, κ-opioid receptor [8]
Endorphins
α-Endorphin YGGFMTSEKSQTPLVT μ-opioid receptor, unknown affinity for other opioid receptors [8]
β-Endorphin YGGFMTSEKSQTPLVTLFKNAIIKNAYKKGE μ-opioid receptor†‡, δ-opioid receptor† [8][9][10][7]
γ-Endorphin YGGFMTSEKSQTPLVTL μ-opioid receptor, unknown affinity for other opioid receptors [8]
Dynorphins
Dynorphin A YGGFLRRIRPKLKWDNQ κ-opioid receptor†‡ [8][9][11]
Dynorphin A1–8 YGGFLRRI κ-opioid receptor, μ-opioid receptor (partial agonist at δ-opioid receptor) [12][13]
Dynorphin B YGGFLRRQFKVVT κ-opioid receptor [8][9]
Big dynorphin YGGFLRRIRPKLKWDNQKRYGGFLRRQFKVVT κ-opioid receptor†‡ [11][14][15]
Leumorphin YGGFLRRQFKVVTRSQEDPNAYYEELFDV κ-opioid receptor [16][17][18][19]
α-Neoendorphin YGGFLRKYPK κ-opioid receptor [8][9]
β-Neoendorphin YGGFLRKYP κ-opioid receptor [8]
Nociceptin
Nociceptin FGGFTGARKSARKLANQ nociceptin receptor†‡ [8][9][20]
Endomorphins
Endomorphin-1 YPWF-NH2 μ-opioid receptor [8][9]
Endomorphin-2 YPFF-NH2 μ-opioid receptor [8][9]
† This symbol next to a receptor indicates that the corresponding peptide is a principal endogenous agonist of the receptor in humans.
‡ This symbol next to a receptor indicates that the corresponding peptide is the endogenous ligand with the highest known potency for the receptor in humans.

Exogenous

Exogenous opioid substances are called exorphins, as opposed to endorphins. Exorphins include opioid food peptides like Gluten exorphin and opioid food peptides and are mostly contained in cereals and animal milk. Exorphins mimic the actions of endorphins by binding to an activating opioid receptors in the brain.

Common exorphins include:

  • Casomorphin (from casein found in milk of mammals, including cows)
  • Gluten exorphin (from gluten found in cereals wheat, rye, barley)
  • Gliadorphin/gluteomorphin (from gluten found in cereals wheat, rye, barley)
  • Soymorphin-5 (from soybean)
  • Rubiscolin (from spinach)

Amphibian

Synthetic

References

  1. ↑ 1.0 1.1 "Structure, tissue distribution, and chromosomal localization of the prepronociceptin gene". Proc. Natl. Acad. Sci. U.S.A. 93 (16): 8666–70. August 1996. doi:10.1073/pnas.93.16.8666. PMID 8710928. Bibcode: 1996PNAS...93.8666M. 
  2. ↑ "Structural organization of human genomic DNA encoding the pro-opiomelanocortin peptide". Proc. Natl. Acad. Sci. U.S.A. 77 (8): 4890–4. August 1980. doi:10.1073/pnas.77.8.4890. PMID 6254047. PMC 349954. Bibcode: 1980PNAS...77.4890C. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=6254047. 
  3. ↑ "Isolation, primary structure, and synthesis of alpha-endorphin and gamma-endorphin, two peptides of hypothalamic-hypophysial origin with morphinomimetic activity". Proc. Natl. Acad. Sci. U.S.A. 73 (11): 3942–6. November 1976. doi:10.1073/pnas.73.11.3942. PMID 1069261. PMC 431275. Bibcode: 1976PNAS...73.3942L. http://www.pubmedcentral.nih.gov/pagerender.fcgi?tool=pmcentrez&artid=431275&pageindex=1. 
  4. ↑ "Isolation and structural organization of the human preproenkephalin gene". Nature 297 (5865): 431–4. June 1982. doi:10.1038/297431a0. PMID 6281660. Bibcode: 1982Natur.297..431N. 
  5. ↑ "Isolation and structural organization of the human preproenkephalin B gene". Nature 306 (5943): 611–4. December 1983. doi:10.1038/306611a0. PMID 6316163. Bibcode: 1983Natur.306..611H. 
  6. ↑ "Endogenous morphine: up-to-date review 2011". Folia Biol. (Praha) 58 (2): 49–56. 2012. PMID 22578954. http://fb.cuni.cz/file/5635/FB2012A0008.pdf. "Positive evolutionary pressure has apparently preserved the ability to synthesize chemically authentic morphine, albeit in homeopathic concentrations, throughout animal phyla. ... The apparently serendipitous finding of an opiate alkaloid-sensitive, opioid peptide-insensitive, µ3 opiate receptor subtype expressed by invertebrate immunocytes, human blood monocytes, macrophage cell lines, and human blood granulocytes provided compelling validating evidence for an autonomous role of endogenous morphine as a biologically important cellular signalling molecule (Stefano et al., 1993; Cruciani et al., 1994; Stefano and Scharrer, 1994; Makman et al., 1995). ... Human white blood cells have the ability to make and release morphine". 
  7. ↑ 7.0 7.1 "μ receptor". IUPHAR/BPS Guide to PHARMACOLOGY. International Union of Basic and Clinical Pharmacology. 15 March 2017. http://www.guidetopharmacology.org/GRAC/ObjectDisplayForward?objectId=319. "Comments: β-Endorphin is the highest potency endogenous ligand ... Morphine occurs endogenously [117].. ...
    Principal endogenous agonists (Human)
    β-endorphin (POMC, P01189), [Met]enkephalin (PENK, P01210), [Leu]enkephalin (PENK, P01210)"     
  8. ↑ 8.00 8.01 8.02 8.03 8.04 8.05 8.06 8.07 8.08 8.09 8.10 8.11 8.12 8.13 "Opioid glycopeptide analgesics derived from endogenous enkephalins and endorphins". Future Medicinal Chemistry 4 (2): 205–226. February 2012. doi:10.4155/fmc.11.195. PMID 22300099. "Table 1: Endogenous opioid peptides". 
  9. ↑ 9.0 9.1 9.2 9.3 9.4 9.5 9.6 9.7 9.8 "Opioid receptors: Introduction". IUPHAR/BPS Guide to PHARMACOLOGY. International Union of Basic and Clinical Pharmacology. 10 August 2015. http://www.guidetopharmacology.org/GRAC/FamilyIntroductionForward?familyId=50. 
  10. ↑ 10.0 10.1 10.2 "δ receptor". IUPHAR/BPS Guide to PHARMACOLOGY. International Union of Basic and Clinical Pharmacology. 15 May 2017. http://www.guidetopharmacology.org/GRAC/ObjectDisplayForward?objectId=317. "Principal endogenous agonists (Human)
    β-endorphin (POMC, P01189), [Leu]enkephalin (PENK, P01210), [Met]enkephalin (PENK, P01210)"     
  11. ↑ 11.0 11.1 "κ receptor". IUPHAR/BPS Guide to PHARMACOLOGY. International Union of Basic and Clinical Pharmacology. 21 February 2017. http://www.guidetopharmacology.org/GRAC/ObjectDisplayForward?objectId=318. "Comments: Dynorphin A and big dynorphin are the highest potency endogenous ligands ...
    Principal endogenous agonists (Human)
    big dynorphin (PDYN, P01213), dynorphin A (PDYN, P01213)"     
  12. ↑ "Dynorphin A 1–8". Dynorphin A 1–8. Human Metabolome Database. 27 September 2017. http://www.hmdb.ca/metabolites/HMDB0012933. Retrieved 20 October 2017. "Dynorphin A (1–8) is a fraction of Dynorphin A with only Tyr-Gly-Gly-Phe-Leu-Arg-Arg-Ile peptide chain.". 
  13. ↑ "Dynorphin A-(1–8): Biological activity". IUPHAR/BPS Guide to PHARMACOLOGY. International Union of Basic and Clinical Pharmacology. http://www.guidetopharmacology.org/GRAC/LigandDisplayForward?tab=biology&ligandId=1621. 
  14. ↑ "Big dynorphin: Biological activity". IUPHAR/BPS Guide to PHARMACOLOGY. International Union of Basic and Clinical Pharmacology. http://www.guidetopharmacology.org/GRAC/LigandDisplayForward?tab=biology&ligandId=3669. "Principal endogenous agonists at κ receptor" 
  15. ↑ "Big dynorphin: Structure – Peptide Sequence". IUPHAR/BPS Guide to PHARMACOLOGY. International Union of Basic and Clinical Pharmacology. http://www.guidetopharmacology.org/GRAC/LigandDisplayForward?tab=structure&ligandId=3669. "Peptide sequence
    YGGFLRRIRPKLKWDNQKRYGGFLRRQFKVVT"     
  16. ↑ "30 years of dynorphins—new insights on their functions in neuropsychiatric diseases". Pharmacology & Therapeutics 123 (3): 353–370. September 2009. doi:10.1016/j.pharmthera.2009.05.006. PMID 19481570. 
  17. ↑ "Dynorphin B (1-29)". Dynorphin B (1-29). United States National Library of Medicine – National Center for Biotechnology Information. 23 December 2017. https://pubchem.ncbi.nlm.nih.gov/compound/16131065. Retrieved 28 December 2017. 
  18. ↑ "Human leumorphin is a potent, kappa opioid receptor agonist". Neuroscience Letters 50 (1–3): 49–52. September 1984. doi:10.1016/0304-3940(84)90460-9. PMID 6149506. 
  19. ↑ "Kappa-selective agonists decrease postsynaptic potentials and calcium components of action potentials in the supraoptic nucleus of rat hypothalamus in vitro". Neuroscience 58 (2): 331–340. January 1994. doi:10.1016/0306-4522(94)90039-6. PMID 7908725. 
  20. ↑ "NOP receptor". IUPHAR/BPS Guide to PHARMACOLOGY. International Union of Basic and Clinical Pharmacology. 18 August 2017. http://www.guidetopharmacology.org/GRAC/ObjectDisplayForward?objectId=320. "Natural/Endogenous Ligands
    nociceptin/orphanin FQ"     

External links

This article incorporates text from the public domain Pfam and InterPro: IPR006024



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