Separation, identification and chelation mechanism of novel zinc-chelating peptides from soybean protein enzymatic hydrolysate

This study aimed to separate and identify novel zinc-chelating peptides from soybean protein hydrolysate obtained by trypsin, and investigate the mechanism of soybean peptide chelating zinc ion. The fraction F323, possessing strong zinc-chelating ability with a chelation rate of 87.19 % ± 0.91 %, was separated by ultrafiltration, gel filtration chromatography and anion-exchange chromatography. Six identified peptides were selected and predicted to be negatively charged and have good water solubility. All these peptides showed zinc-chelating activity, among which EEGQQQGEQR, VFDGELQEGR, and EEQEWPR exhibited the highest zinc-chelating capacity. EEGQQQGEQR tended to form a more ordered structure after chelating zinc ions. FTIR spectra showed that amide groups and carboxyl groups in the three peptides were likely involved in the chelation. Molecular dynamics simulation results revealed that the amino acid residues in soybean peptides participating in the chelation of zinc ion were mainly glutamic acid (Glu, E), then aspartic acid (Asp, D) and glutamine (Gln, Q). The carboxyl oxygens in the side chain groups of Glu(E) and Asp(D), and the carbonyl oxygen of peptide bond were involved in the coordination with zinc ion. These results provide theoretical foundations for the preparation of zinc-chelating peptides from soybean protein, and the development of peptide-zinc chelates used as zinc supplements.