Preparation, Purification and Characterization of Antibacterial and ACE Inhibitory Peptides from Head Protein Hydrolysate of Kuruma Shrimp, <i>Marsupenaeus japonicus</i>

Kuruma shrimp (Marsupenaeus japonicus) heads, as the main by-product of the seafood processing industry, are rich in underutilized high-quality protein. After papain hydrolysis at 50 °C for 4 h, the protein hydrolysate of shrimp heads was found to show notable antibacterial and angiotensin I-converting enzyme (ACE) inhibitory activities. After purification using two stages of revered-phase high-performance liquid chromatography (RP-HPLC), the antibacterial peptide VTVP and the ACE inhibitory peptide ARL/I were successfully identified from most active fractions by LC–MS/MS. Peptide VTVP was a desirable hydrophobic peptide, with a MIC value in the range from 1.62 to 8.03 mM against all tested pathogens. Peptide ARL/I exhibited potent ACE inhibitory activity, with an IC50 value of 125.58 µM, and was found to be a competitive inhibitor based on the Lineweaver–Burk plot. Moreover, the result of the molecular docking simulation indicated that the interaction binding between ARL/I and ACE was mainly stabilized by hydrogen bonds, as well as forming a coordinate bond with the Zn2+ site. The purified peptides did not show hemolytic activity toward rabbit erythrocytes. To sum up, the bioactive peptides isolated from shrimp heads could be applicable for food or pharmaceutical areas as promising ingredients