Table 1 Endogenous mammalian opioid peptides, amino acid sequence, and selectivity for the opioid receptors
From: Opioid system and related ligands: from the past to future perspectives
Endogenous opioid peptide | Amino acid sequence (three-letter code) | Opioid receptor affinity |
|---|---|---|
β-endorphin | Tyr-Gly-Gly-Phe-Met-Thr-Ser-Glu-Lys-Ser-Gln-Thr-Pro-Leu-Val-Thr-Leu-Phe-Lys-Asn- Ala-Ile-Ile-Lys-Asn-Ala-Tyr-Lys-Lys-Gly-Glu | MOR, DOR (MOR = DOR) |
Met-enkephalin | Tyr-Gly-Gly-Phe-Met | DOR, MOR (DOR >  > MOR) |
Leu-enkephalin | Tyr-Gly-Gly-Phe-Leu | |
Dynorphin A | Tyr-Gly-Gly-Phe-Leu-Arg-Arg-Ile-Arg-Pro-Lys-Leu-Lys-Trp-Asp-Asn-Gln | KOR, MOR, DOR |
Dynorphin B | Tyr-Gly-Gly-Phe-Leu-Arg-Arg-Gln-Phe-Lys-Val-Val-Thr | KOR >  > MOR and DOR |
Nociceptin/orphanin FQ | Phe-Gly-Gly-Phe-Thr-Gly-Ala-Arg-Lys-Ser-Ala-Arg-Lys-Leu-Ala-Asn-Gln | NOP |