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Table 5 Opioid peptides generated from the enzymatic hydrolysis of animal and plant proteins in the gastrointestinal tract

From: Protein hydrolysates in animal nutrition: Industrial production, bioactive peptides, and functional significance

Source Name of opioid peptide Amino acid sequence
Milk casein Bovine β-casomorphin 1–3 Tyr-Pro-Phe-OH
Bovine β-casomorphin 1–4 Tyr-Pro-Phe-Pro-OH
Bovine β-casomorphin 1–4, amide Tyr-Pro-Phe-Pro-NH2
Bovine β-casomorphin 5 Tyr-Pro-Phe-Pro-Gly-OH
Bovine β-casomorphin 7 Tyr-Pro-Phe-Pro-Gly-Pro-Ile-OH
Bovine β-casomorphin 8 Tyr-Pro-Phe-Pro-Gly-Pro-Ile-Pro-OHa
Gluten protein Gluten exorphin A5 Gly-Tyr-Tyr-Pro-Thr-OH
Gluten exorphin B4 Tyr-Gly-Gly-Trp-OH
Gluten exorphin C Tyr-Pro-Ile-Ser-Leu-OH
Gliadorphin Tyr-Pro-Gln-Pro-Gln-Pro-Phe-OH
Soybean protein Soymorphin-5b Tyr-Pro-Phe-Val-Val-OH
Soymorphin-5, amide Tyr-Pro-Phe-Val-Val-NH2
Soymorphin-6 Tyr-Pro-Phe-Val-Val-Asn-OH
Soymorphin-7 Tyr-Pro-Phe-Val-Val-Asn-Ala-OH
Spinach protein Rubiscolin-5 Gly-Tyr-Tyr-Pro-OH
Rubiscolin-6 Gly-Tyr-Tyr-Pro-Thr-OH
  1. Adapted from Li-Chan [21], López-Barrios et al. [22], Shimizu and Son [35], Bah et al. [36], and Froetschel [42]
  2. aAnother form of bovine β-casomorphin 8 has histidine instead of proline in position 8, depending on whether the peptide is derived from A1 or A2 beta-casein
  3. bDerived from β-conglycinin β-subunit