A tripeptide is a peptide made of three amino acids linked together by two peptide bonds.
- “Tri–” means three
- A tripeptide forms when three amino acids join in a specific sequence through peptide bonds (dehydration reactions)
It’s one step more complex than a dipeptide and still considered an oligopeptide — a short-chain peptide.
🔗 How Is a Tripeptide Formed?
- The carboxyl group (-COOH) of the first amino acid bonds with the amino group (-NH₂) of the second.
- Then the second’s carboxyl group bonds with the third’s amino group.
- This forms two peptide bonds and releases two molecules of water (H₂O).
🧪 Examples of Tripeptides
| Tripeptide | Amino Acids | Function |
|---|---|---|
| Glutathione | Glutamate + Cysteine + Glycine | Powerful antioxidant, detoxification, immune function |
| TRH | Glutamic acid + Histidine + Proline | Stimulates TSH and prolactin from the pituitary |
| L-carnosine (dipeptide often combined into tripeptide forms in supplements) | Brain and muscle antioxidant |
🔬 Biological Importance
- Tripeptides are involved in:
- Antioxidant defense (e.g., glutathione neutralizes free radicals)
- Hormonal regulation (e.g., TRH triggers thyroid hormone pathways)
- Immune system support
- Cell signaling and metabolic regulation
- Many tripeptides are also rapidly absorbed and utilized by the body, making them useful in medical and nutritional therapies.
🍽️ Tripeptides in Digestion
- Proteins are broken down into smaller peptides (including tripeptides) during digestion.
- Tripeptides are absorbed efficiently in the small intestine via PEPT1 transporters.
- Once inside cells, they may:
- Be further broken down into amino acids
- Be used directly for signaling or metabolic purposes
🧠 Summary Table:
| Feature | Tripeptide |
|---|---|
| Composition | 3 amino acids |
| Bonds | 2 peptide bonds |
| Type | Oligopeptide |
| Biological roles | Antioxidant, hormonal, immune, metabolic signaling |
| Common examples | Glutathione, TRH |
| Importance in health | Detoxification, hormone regulation, cell protection |