Sardine Peptide (Valyl-Tyrosine)

Sardine Peptide (Valyl-Tyrosine, Val-Tyr) is a bioactive dipeptide derived from enzymatic hydrolysis of sardine (Sardinops melanostictus) muscle protein. It is not a macronutrient source in typical supplemental doses. Key details: **Molecular composition:** Dipeptide consisting of L-Valine and L-Tyrosine linked by a peptide bond; molecular weight ~280.32 Da. **Amino acid content per molecule:** L-Valine (branched-chain amino acid, ~117.15 Da portion) and L-Tyrosine (aromatic amino acid, ~181.19 Da portion). **Typical supplemental dose:** 400–600 µg Val-Tyr per serving (standardized sardine peptide supplements often deliver ~400 µg of the active dipeptide). **Bioactive compound:** Val-Tyr acts as a natural angiotensin-converting enzyme (ACE) inhibitor with an IC50 of approximately 26 µM, contributing to its antihypertensive activity. **Protein content:** Negligible at supplemental doses (micrograms); the parent sardine hydrolysate powder may contain ~80–90% protein by weight, but the isolated dipeptide is used for its pharmacological rather than nutritional protein value. **Micronutrients from parent hydrolysate:** Trace amounts of marine-derived minerals including selenium (~10–30 µg per gram of crude hydrolysate), zinc (~0.5–1.5 mg/g hydrolysate), phosphorus, and omega-3 fatty acid residues, though purified Val-Tyr preparations contain negligible mineral content. **Vitamins:** Not a significant source of vitamins; parent sardine material contains vitamin B12 (~8–12 µg/100g) and vitamin D3 (~4–8 µg/100g), but these are largely removed during peptide purification. **Bioavailability notes:** Val-Tyr dipeptide demonstrates high oral bioavailability (~70–80%) due to its small molecular size, enabling intact absorption via intestinal PepT1 (H⁺-coupled peptide transporter) without requiring further enzymatic digestion. It resists degradation by gastrointestinal proteases better than larger peptides. Peak plasma concentration is achieved within approximately 30–60 minutes post-ingestion. The dipeptide is partially hydrolyzed to free valine and tyrosine in enterocytes and plasma, but a significant fraction reaches target tissues (vascular endothelium, brain) in intact dipeptide form, which is essential for its ACE-inhibitory bioactivity. Tyrosine released from hydrolysis serves as a precursor to catecholamines (dopamine, norepinephrine) and thyroid hormones, contributing to neurotransmitter and metabolic regulation.