Separation and identification of zinc-chelating peptides from sesame protein hydrolysate using IMAC-Zn2+ and LC–MS/MS

The metal chelating peptides from sesame protein hydrolysates (SPH), treated by papain, alcalase and trypsin, respectively, were investigated. The hydrolysates treated by trypsin had the highest metal chelating ability. The metal chelating peptides were isolated from the trypsin hydrolysates using immobilized metal affinity chromatography (IMAC-Zn2+). Further, six zinc-chelating peptides were identified with reversed phase (RP)-HPLC and mass spectrometry (LC–MS/MS). Three of these metal-chelating peptides, Ser-Met, Leu-Ala-Asn and Asn-Cys-Ser, were synthesized and the metal-chelating ability of peptides was measured. The Asn-Cys-Ser peptide showed the highest zinc and iron chelating ability, which was even higher than reduced glutathione (GSH). The results confirm that the zinc or iron chelating activity of these peptides, and provide further support to its feasibility as natural metal chelating agents from sesame protein.