Structures of selected endogenous opioid peptides
| [Leu5]enkephalin | Tyr-Gly-Gly-Phe-Leu |
| [Met5]enkephalin | Tyr-Gly-Gly-Phe-Met |
| Dynorphin A | Tyr-Gly-Gly-Phe-Leu-Arg-Arg-Ile-Arg–Pro-Lys–Leu-Lys-Trp-Asp-Asn-Gln |
| Dynorphin B | Tyr-Gly-Gly-Phe-Leu-Arg-Arg-Gln-Phe-Lys-Val-Val-Thr |
| a-Neoendorphin | Tyr-Gly-Gly-Phe-Leu-Arg-Lys-Tyr-Pro-Lys |
| β-Neoendorphin | Tyr-Gly-Gly-Phe-Leu-Arg-Lys-Tyr-Pro |
| βh-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 |
| Endomorphin-1 | Tyr-Pro-Trp-Phe-NH2 |
| Endomorphin-2 | Tyr-Pro-Phe-Phe-NH2 |
| Orphanin FQ/nociceptin | Phe-Gly-Gly-Phe-Thr-Gly-Ala-Arg-Lys-Ser-Ala-Arg-Lys-Leu-Ala-Asn-Gln |