Table 1.
Sequences and affinity of endogenous and exogenous opioid peptides
| Precursor | Peptide | Sequence | Receptor affinity |
|---|---|---|---|
| Pro-opiomelanocortin | 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 > KOR |
| Pro-enkephalin | [Met5]Enkephalin | Tyr-Gly-Gly-Phe-Met | DOR > MOR ≫ KOR |
| [Leu5]Enkephalin | Tyr-Gly-Gly-Phe-Leu | ||
| Pro-dynorphin | Dynorphin A | Tyr-Gly-Gly-Phe-Leu-Arg-Arg-Ile-Arg-Pro-Lys-Trp-Asp-Asn-Gln | KOR ≫ MOR > DOR |
| Dynorphin B | Tyr-Gly-Gly-Phe-Leu-Arg-Arg-Gln-Phe-Lys-Val-Val-Thr | ||
| α-neomorphin | Tyr-Gly-Gly-Phe-Leu-Arg-Lys-Tyr-Pro-Lys | ||
| β-neomorphin | Tyr-Gly-Gly-Phe-Leu-Arg-Lys-Tyr-Pro | ||
| Unknown | Endomorphin-1 | Tyr-Pro-Trp-Phe-NH2 | MOR |
| Endomorphin-2 | Tyr-Pro-Phe–Phe-NH2 | MOR | |
| κ-casein | Casoxin 4 | Tyr-Pro-Ser-Tyr-OCH3 | MOR |
| β-conglycinin | Soymorphin-5 | Tyr-Pro-Phe-Val-Val | MOR |
| Soymorphin-6 | Tyr-Pro-Phe-Val-Val-Asn | ||
| Soymorphin-7 | Tyr-Pro-Phe-Val-Val-Asn-Ala |