Identification of iron-chelating peptides from Pacific cod skin gelatin and the possible binding mode

- Pacific cod skin gelatin is a good source to produce iron-chelating peptides.
- The 240-min gelatin tryptic hydrolysates possessed higher iron-chelating activity.
- GPAGPHGPPGKDGR, AGPHGPPGKDGR and AGPAGPAGAR exhibited high affinity to iron.
- The complexation of peptides with ferrous ions was mainly at the ratio of 1:1.
- Peptide backbone and arginine side chain participated in the iron coordination.

Pacific cod skin gelatin was hydrolyzed under optimized conditions (trypsin, 240 min) to generate iron-chelating peptides. Gelatin tryptic hydrolysates were purified by immobilized metal affinity chromatography and reversed phase high performance liquid chromatography. Three novel iron-chelating peptides identified by LC-HRMS/MS were GPAGPHGPPGKDGR, AGPHGPPGKDGR and AGPAGPAGAR, which exhibited high affinity to ferrous ions. The iron-peptide complexation, investigated by ESI-MS and FTIR spectroscopy, showed that the three peptides bound with iron mainly at the ratio of 1:1. Among the groups of the three peptides, the amino and carboxylate terminal groups and peptide bond from peptide backbone, as well as the amino and imine from arginine side chain were involved in the complexation. Moreover, several amino acid side chain groups of GPAGPHGPPGKDGR and AGPHGPPGKDGR, including amino (Lys), imine (His) and carboxylate (Asp), supplied additional iron binding sites. This study suggests a potential application of gelatin-derived peptides as novel carriers to combat iron deficiency.