Hydrolysis Characteristics of Pinctada fucata Meat Protein and Screening for Angiotensin-Converting Enzyme Inhibitory Peptides

This study aimed to explore the hydrolysis characteristics of Pinctada fucata meat and quick identification of angiotensin-converting enzyme (ACE) inhibitory peptides from its hydrolysates. Hydrolysates at different times (2, 4, 6, 8 and 10 h) were collected to characterize the hydrolyis process by tricine-sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and molecular mass distribution measurement, and reversed-phase high performance liquid chromatography (RP-HPLC). In addition, the 10 h hydrolysate was separated and purified, and then the fractions with a high ACE inhibitory activity were identified and screened by molecular docking. Moreover, their activities were verified and their mechanisms of action were elucidated. The results showed that as the hydrolysis proceeded, large-molecular-mass proteins were gradually digested into low-molecular-mass peptides, and that a characteristic peak appeared in the RP-HPLC profile. A total of 54 peptide sequences with high average local confidence (ALC) were obtained from fractions F2 and F3, which had stronger ACE inhibitory activities. Six potential ACE inhibitory peptides were determine by molecular docking and five of them exhibited different ACE inhibitory activities at 1 mg/mL, among which, WFHAVFW and WHAFLW had the strongest ACE inhibitory activity with inhibition percentages of (95.57 ± 0.37)% and (98.59 ± 0.08)%, respectively. The half-maximal inhibition concentration (IC₅₀) value of the hexapeptide WHAFLW was determined to be 52.39 μmol/L. The molecular docking indicated that the peptides could interact with ACE through hydrogen bonding, van der Waals interaction, and Pi-Pi interaction to form a stable peptide-enzyme complex. In conclusion, the combined use of bioactivityguided fractionation and computer-aided screening can provide a rapid method for screening hydrolysate for strong ACE inhibitory peptides.