TABLE 1

Endogenous opioid peptides

Receptor Precursor Endogenous Peptide Amino Acid Sequence Source References
μ (MOR, OP3) Pro-opiomelanocortin β-endorphin Tyr-Gly-Gly-Phe-Met-Thr-Ser-Glu-Lys-Ser-Gln-Thr-Pro-Leu-Val-Thr-Leu-Phe-Lys-A sn-Ala-Ile-Ile-Lys-Asn-Ala-Tyr-Lys-Lys-Gly-Glu Mammalian brain Li and Chung (1976)
β-Casein (bovine) β-Casomorphin-5 Tyr-Pro-Phe-Pro-Gly Bovine milk Blanchard et al. (1987)
β-Casomorphin-7 Tyr-Pro-Phe-Pro-Gly-Pro-Ile
Morphiceptin Tyr-Pro-Phe-Pro-NH2
β-Casein (human) β-Casomorphin-5 Tyr-Pro-Phe-Val-Glu Human milk Blanchard et al. (1987)
β-Casomorphin-7 Tyr-Pro-Phe-Val-Glu-Pro-Ile
Hemoglobin Hemorphin-4 Tyr-Pro-Trp-Thr Human blood Nyberg et al. (1997); Zhao et al. (1997)
Hemorphin-7 Tyr-Pro-Trp-Thr-Gln-Arg-Phe
Unknown Dermorphin Tyr-D-Ala-Phe-Gly-Tyr-Pro-Ser-NH2 Frog skin Bozu et al. (1997)
Unknown Endomorphin-1 Tyr-Pro-Trp-Phe-NH2 Bovine brain, human brain cortex Hackler et al. (1997); Zadina et al. (1997)
Endomorphin-2 Tyr-Pro-Phe-Phe-NH2
Unknown Tyr-MIF-1 Tyr-Pro-Leu-Gly-NH2 Bovine brain, human brain cortex Zadina et al. (1994)
Tyr-W-MIF-1 Tyr-Pro-Trp-Gly-NH2
δ (DOR, OP1) Proenkephalin [Met5]enkephalin Tyr-Gly-Gly-Phe-Met Mammalian brain Hughes et al. (1975)
[Leu5]enkephalin Tyr-Gly-Gly-Phe-Leu
Tyr-Gly-Gly-Phe-Met-Arg-Phe
Tyr-Gly-Gly-Phe-Met-Arg-Gly-Leu
Unknown Dermenkephalin Tyr-D-Met-Phe-His-Leu-Met-AspNH2 Frog skin Amiche et al. (1989); Kreil et al. (1989)
Deltorphin-I Tyr-D-Ala-Phe-Asp-Val-Val-Gly-NH2
Deltorphin-II Tyr-D-Ala-Phe-Glu-Val-Val-Gly-NH2
κ (KOR, OP2) Prodynorphin Dynorphin A Tyr-Gly-Gly-Phe-Leu-Arg-Arg-Ile-Arg-Pro-Lys-Leu-Lys-Trp-Asp-Asn-Gln Mammalian brain Chavkin et al. (1982)
Tyr-Gly-Gly-Phe-Leu-Arg-Arg-Ile
Dynorphin A(1-8) Tyr-Gly-Gly-Phe-Leu-Arg-Arg-Gln-Phe-Lys-Val-Val-Thr
Dynorphin B
ORL1 (NOP1) Pronociceptin Nociceptin/orphanin FQ Phe-Gly-Gly-Phe-Thr-Gly-Ala-Arg-Lys-Ser-Ala-Arg-Lys-Leu-Ala-Asn-Gln Mammalian brain Meunier et al. (1995); Reinscheid et al. (1995)