Preparation, purification and identification of iron-chelating peptides derived from tilapia (Oreochromis niloticus) skin collagen and characterization of the peptide-iron complexes

Tilapia skin collagen was hydrolyzed by five proteases (trypsin, pepsin, neutral protease, alkaline protease and protamex). The results showed that the tilapia skin collagen hydrolysate (TSCH) obtained by 2 h hydrolysis with trypsin exhibited the highest iron chelating rate. The TSCH was then separated by immobilized metal affinity chromatography (IMAC-Fe 2+ ) and obtained the tilapia skin collagen iron-chelating peptides (TSCICP). The iron chelating sites of TSCICP were corresponding to carboxylic groups of Asp/Glu and guanidine nitrogen of Arg/Lys. After chelated with iron ions, TSCICP was folded and aggregated to form spherical particles with increased particle size. The TSCICP-iron complexes could maintain high iron solubility at various pH and in simulated gastrointestinal digestion. The iron bio-accessibility of TSCICP-iron complexes was high than that of ferrous glycinate and ferrous sulfate. Finally, TSCICP was purified by RP-HPLC and identified by LC-MS/MS. Four iron-chelating peptides were identified as GPAGPAGEK (782.39 Da), DGPSGPKGDR (984.46 Da), GLPGPSGEEGKR (1198.59 Da) and DGPSGPKGDRGETGL (1441.68 Da). These results indicating that the iron-chelating peptides derived from tilapia skin collagen could be used as potential dietary iron supplement. • TSCICP were isolated from TSCH by utilizing IMAC-Fe 2+ . • The iron chelating sites of TSCICP corresponded to the Asp, Glu, Arg and Lys. • Iron induced the structural folding and aggregation of TSCICP. • TSCICP-iron complexes had the property of high iron solubility. • Four iron-chelating peptides sequences were identified from TSCICP.