Opioid peptide

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Vertebrate endogenous opioids neuropeptide
Symbol Opiods_neuropep
Pfam PF01160
InterPro IPR006024
Structural correlation between met-enkephalin, an opioid peptide, (left) and morphine, an opiate drug, (right)

Opioid peptides are short sequences of amino acids 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, and the control of food intake.

Opioid-like peptides may also be absorbed from partially digested food (casomorphins, exorphins, and rubiscolins). The opioid food peptides have lengths of typically 4-8 amino acids. The body's own 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 opioids produced by the body [edit]

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

Opioid food peptides[edit]

Amphibian opioid peptides[edit]

Synthetic opioid peptides[edit]


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  2. ^ Chang AC, Cochet M, Cohen SN (August 1980). "Structural organization of human genomic DNA encoding the pro-opiomelanocortin peptide". Proc. Natl. Acad. Sci. U.S.A. 77 (8): 4890–4. doi:10.1073/pnas.77.8.4890. PMC 349954free to read. PMID 6254047. 
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  4. ^ Noda M, Teranishi Y, Takahashi H, Toyosato M, Notake M, Nakanishi S, Numa S (June 1982). "Isolation and structural organization of the human preproenkephalin gene". Nature. 297 (5865): 431–4. doi:10.1038/297431a0. PMID 6281660. 
  5. ^ Horikawa S, Takai T, Toyosato M, Takahashi H, Noda M, Kakidani H, et al. (Dec 1983). "Isolation and structural organization of the human preproenkephalin B gene". Nature. 306 (5943): 611–4. doi:10.1038/306611a0. PMID 6316163. 
  6. ^ Stefano GB, Ptáček R, Kuželová H, Kream RM (2012). "Endogenous morphine: up-to-date review 2011" (PDF). Folia Biol. (Praha). 58 (2): 49–56. PMID 22578954. 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 

External links[edit]

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