Preparation, Separation, and Identification of Low-Bitter ACE-Inhibitory Peptides from Sesame (Sesamum indicum L.) Protein

To prepare and characterize low-bitter angiotensin-converting enzyme (ACE)-inhibitory peptides from sesame protein, a triple-enzyme hydrolysis system was optimized using mixture design and response surface methodology. The resulting hydrolysate was separated by ultrafiltration and medium-pressure chromatography, followed by identification through nano-liquid chromatography-electrospray ionization-tandem mass spectrometry. Finally, the mechanism of typical low-bitter ACE-inhibitory peptides was elucidated by molecular docking and molecular dynamics simulation. Results showed that the optimal enzyme activity ratio of 1:0.94:1.07 for Alcalase, trypsin, and Flavourzyme, combined with optimized hydrolysis conditions (E/S ratio of 126,793.03 nkat/g, pH 8.40, 4.82 h hydrolysis time, and 45 °C), resulted in a peptide yield of 93.19 ± 0.14%, ACE-inhibitory rate of 95.92 ± 0.23%, and bitter value of 3.15 ± 0.09. APQLGR and APWLR exhibited high ACE-inhibitory activity and minimal bitterness among the seventeen identified peptides. Although both peptides bound to the S1 pocket and Zn²⁺ catalytic site of ACE, APWLR exhibited an additional interaction with the S2 pocket. Both peptides were predicted to antagonize the bitter taste receptor T2R14 by forming stable complexes with key residues, but two complexes exhibited distinct mechanisms of stabilization. This work demonstrates a method for producing dual-functional peptides from sesame protein, paving the way for their application in functional foods.