Characterization of Allium tuberosum Rottl. peptides with dual inhibitory activities against angiotensin I converting enzyme and dipeptidyl peptidase-IV

Two peptides with dual functionality, namely LLPSY and NAPALVY, exhibit inhibitory effects on both angiotensin-I-converting enzyme (ACE) and dipeptidyl peptidase-IV (DPP-IV), were successfully identified from the hydrolysates of Chinese chive seed (Allium tuberosum Rottl.). Peptide isolation involved reversed-phase chromatography, and peptide sequences were characterized through liquid chromatography-tandem mass spectrometry analysis and de novo sequencing. Notably, the Lineweaver-Burk plot analysis revealed that LLPSY (IC₅₀: 15.66 ± 1.11 µM) acted in a non-competitive manner, whereas NAPALVY (IC₅₀: 3.42 ± 0.79 µM) exhibited competitive inhibition, potently inhibiting ACE. Their stability tests against ACE further revealed that LLPSY acted as a real substrate, while NAPALVY functioned as a true inhibitor of ACE. In terms of DPP-IV inhibition, LLPSY (IC₅₀: 2.48 ± 0.10 mM) was identified as a competitive inhibitor, whereas NAPALVY (IC₅₀: 7.63 ± 0.52 mM) displayed noncompetitive inhibition. Both peptides exhibited true inhibitory effects on DPP-IV. Docking simulations provided insights into peptide-enzyme interactions. These novel Allium tuberosum Rottl.-derived peptides hold promise for controlling blood pressure and blood glucose.