Mining for Novel Umami Peptides from Sea Cucumber Viscera Hydrolysate with ACE Inhibitory Activity

Flavor-enhancing characteristics of umami peptides have garnered considerable interest, while their functionality has received limited attention. This study screened umami peptides from sea cucumber viscera hydrolysate and further explored peptides with angiotensin converting enzyme (ACE) inhibitory activity. The amino acid sequences of the prepared hydrolysate were identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS), and three umami peptides were mined. These peptides were synthesized for evaluating their ACE inhibitory activity, among which NSPGDSFP exhibited the strongest activity with an IC₅₀ value of 15.92 ± 0.68 μg/mL. NSPGDSFP demonstrated a noncompetitive action mode and resistance to gastrointestinal environments. Molecular docking revealed that it binds to ACE through hydrogen bonds and hydrophobic interactions. Biolayer interferometry assay further demonstrated that NSPGDSFP binds to ACE with an affinity constant K_D of 2.64 × 10^-8 M. Additionally, NSPGDSFP demonstrated umami-enhancement effect associated with varying levels of salt concentration. The affinity of NSPGDSFP for umami receptor T1R1/T1R3 is primarily contributed by hydrogen bonds. Molecular dynamics (MD) simulation analysis was conducted to further validate the stability of the binding complexes formed between NSPGDSFP and ACE, as well as between NSPGDSFP and the T1R1/T1R3 receptor complex. This study lays the foundation for the future exploration of umami peptide as a food seasoning additive with antihypertension effects.