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

Abstract

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-Fe2+) 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.