Insight into the interaction between aromatic ACE-inhibitory tetrapeptide (YKYY) from wakame with human serum albumin

Understanding the binding of serum albumin (SA) to food-derived bioactive compounds is crucial for developing functional foods with disease-intervention potential. This study investigated the interaction between the new angiotensin-converting enzyme (ACE) inhibitory peptide (ACEIP) Tyr-Lys-Tyr-Tyr (YKYY), derived from wakame (Undaria pinnatifida), and human serum albumin (HSA) using multispectral techniques, molecular docking, and molecular dynamics simulations. Multispectral analysis revealed that YKYY binding enhanced the hydrophobicity of Trp residues and raised the α-helix content by approximately 14%, which increased the compactness of HSA conformation. Specific site fluorescent probe competition experiments indicated that YKYY preferentially binds to Site I of HSA, which helps to maintain its structural stability. Thermodynamic analysis demonstrated that YKYY binds spontaneously to HSA with a moderate binding constant (K_a = 1.95 (± 0.37) × 10⁶ M^-1) at 303 K, with ΔG⁰ = -36.49 (±1.65) kJ/mol, ΔH⁰ = -234.96 (±10.03) kJ/mol, and ΔS⁰ = -655 (±0.02) J/mol/K for the binding process. Molecular simulations further confirmed that the stability of the YKYY-HSA complex is maintained through hydrogen bonding, hydrophobic interactions, and van der Waals forces. These findings provide mechanistic insights into the YKYY-HSA interaction and maybe offer a potential reference model for understanding the biophysical stability of SA in complex with Tyr containing ACEIPs.