Preparation and identification of peptides and their zinc complexes with antimicrobial activities from silver carp (Hypophthalmichthys molitrix) protein hydrolysates

- Flavourzyme hydrolysates were suitable for preparing antibacterial zinc complexes.
- The zinc chelating peptides were identified by nano-LC-ESI-MS.
- Peptide sequences with more acidic amino acid residues bound more zinc ions.
- The number of zinc in complex was positively related to its antibacterial activity.
- YEESQAELEGSLK-zinc complex has high antibacterial activity.

The antibacterial activities of peptide-zinc complexes (PZCs) prepared from silver carp (Hypophthalmichthys molitrix) protein hydrolysates treated by four enzymes were evaluated. PZCs prepared from flavourzyme hydrolysates exhibited the highest antibacterial activities. The peptides that were able to produce PZCs with high antibacterial activity were isolated from flavourzyme hydrolysates using chromatographic procedures. Eleven peptides were identified through nano-liquid chromatography-electrospray ionization mass spectrometry. Five of these identified peptides were synthesized. The PZCs obtained were characterized and tested for antimicrobial activities. Results suggested that all five PZCs present strong antibacterial activities but no antifungal activities. Peptides with more acidic amino acid residues in their sequences could bind more zinc ions than peptides with fewer acidic amino acid residues. Zinc complexes of acidic amino acid-richer peptides showed stronger antibacterial activities. Results confirmed the antibacterial activities of PZCs from silver carp hydrolysates, and suggested the feasibility of PZCs as a provider of natural zinc ligands for antibacterial agents in the food and feed industries.