🔬 What is a Tripeptide?

• A tripeptide is a small peptide molecule made of three amino acids linked together by two peptide bonds.

• Formula:
  Amino acid₁ – Peptide bond – Amino acid₂ – Peptide bond – Amino acid₃

Example: Glycyl-alanyl-serine (Gly-Ala-Ser)

🧩 Structure

1. Amino acids involved – can be any of the 20 standard amino acids.

2. Peptide bonds – formed by condensation (removal of water) between the carboxyl group (–COOH) of one amino acid and the amino group (–NH₂) of the next.

3. Ends of the chain:

   • N-terminus → free amino group at the start.

   • C-terminus → free carboxyl group at the end.

So, a tripeptide always has directionality (N → C).

⚗️ Formation

• Synthesized during protein biosynthesis or chemical synthesis.

• Enzyme involved in cells: ribosome (using mRNA code + tRNA).

• Reaction type: Condensation (dehydration synthesis).

🔑 Properties

• Size: Small molecules compared to proteins (molecular weight ~ 200–500 Da).

• Solubility: Many are water-soluble.

• Charge: Depends on side chains and pH.

• Biological activity: Some tripeptides have strong physiological roles.

🧬 Examples of Natural Tripeptides

1. Glutathione (γ-Glu-Cys-Gly)

   • Most important antioxidant in cells.

   • Protects from free radicals and toxins.

2. Thyrotropin-releasing hormone (TRH, pGlu-His-Pro-NH₂)

   • Hormone secreted by the hypothalamus.

   • Stimulates release of TSH (thyroid-stimulating hormone).

3. Ophthalmic acid (γ-Glu-Ala-Gly)

• Found in eye lens and liver.

• Similar to glutathione but without antioxidant properties.

📌 Functions & Roles

• Cellular protection (e.g., glutathione protects against oxidative stress).

• Regulation (some act as hormones or neurotransmitters).

• Metabolic intermediates (can be further broken down to amino acids).

• Nutritional supplements (easily absorbed compared to whole proteins).

🧪 Laboratory & Medical Relevance

• Biomarkers: Certain tripeptides indicate oxidative stress or liver damage.

• Therapeutics: Tripeptides like glutathione are studied for anti-aging, liver health, and immunity.

• Cosmetics: Some tripeptides stimulate collagen production in skin-care products.

Tripeptide (Glutathione) 

🔹 Generic Name

Glutathione (reduced form, GSH)

🔹 Drug Class

• Antioxidant

• Detoxifying agent

• Cytoprotective peptide

🧪 Chemical Information

• Molecular Formula: C₁₀H₁₇N₃O₆S

• Molecular Weight: 307.32 g/mol

• Structure: Tripeptide made of glutamate, cysteine, and glycine.

⚙️ Mechanism of Action

1. Acts as a major intracellular antioxidant.

2. Neutralizes reactive oxygen species (ROS) and free radicals.

3. Regenerates other antioxidants (Vitamin C, Vitamin E).

4. In liver, conjugates with toxins for excretion (detox pathway).

5. Supports immune function and DNA synthesis.

📌 Indications (Medical Uses)

• Liver disorders (hepatitis, cirrhosis, fatty liver).

• Detoxification (alcohol, drugs, heavy metals, chemotherapy).

• Skin lightening (off-label, cosmetic).

• Neurodegenerative diseases (Parkinson’s, Alzheimer’s – as supportive).

• Boosting immunity in chronic illness.

💉 Dosage & Administration

🔹 Oral Supplements (capsules, tablets, powders):

• Typical dose: 250 mg – 1000 mg daily.

• Bioavailability is limited (sometimes combined with precursors like N-acetylcysteine).

🔹 Intravenous (IV) Injection (medical use & skin lightening):

• Dose: 600 mg – 1200 mg 2–3 times weekly (varies by condition).

• Often given with Vitamin C.

🔹 Inhalation (Nebulized):

• Dose: 600 mg twice daily for respiratory conditions (e.g., COPD, cystic fibrosis).

⚠️ Side Effects

• Generally, well tolerated.

• Mild: Bloating, cramps, headache, skin rash.

• IV use: Rare allergic reactions, bronchospasm (especially in asthmatics).

• Long-term high-dose skin use: May cause renal issues (rare).

🚫 Contraindications

• Known allergy to glutathione.

• Caution in asthma patients (risk of bronchospasm with inhalation).

• Safety in pregnancy & lactation not well established.

💊 Drug Interactions

• May alter effectiveness of chemotherapy drugs (should be supervised by oncologist).

• Works synergistically with Vitamin C, Vitamin E, and NAC.

📦 Available Forms

• Capsules / Tablets (250 mg, 500 mg, 1000 mg).

• IV injection vials (600 mg, 1200 mg).

• Nebulization solution.

• Cosmetic creams/serums (for anti-aging/skin lightening).

📝 Summary

• Tripeptide (Glutathione) = powerful natural antioxidant.

• Formula: C₁₀H₁₇N₃O₆S.

• Dosages: Oral (250–1000 mg/day), IV (600–1200 mg 2–3×/week), Inhaled (600 mg BID).

• Uses: Liver health, detox, immunity, skin lightening (cosmetic), supportive therapy in chronic disease.

• Side effects: Usually mild, rare severe reactions.