Abstract
In this study, three synthetic zinc-chelating peptides (ZCPs) derived from sea cucumber hydrolysates with limited or none of the common metal-chelating amino-acid residues were analyzed by flame atomic absorption spectroscopy, circular dichroism spectroscopy, size exclusion chromatography, zeta-potential, Fourier transform infrared spectroscopy, Raman spectroscopy and nuclear magnetic resonance spectroscopy. The amount of zinc bound to the ZCPs reached maximum values with ZCP:zinc at 1:1, and it was not further increased by additional zinc presence. The secondary structures of ZCPs were slightly altered, whereas no formation of multimers was observed. Furthermore, zinc increased the zeta-potential value by neutralizing the negatively charged residues. Only free carboxyl in C-terminus of ZCPs was identified as the primary binding site of zinc. These results provide the theoretical foundation to understand the mechanism of zinc chelation by peptides.
Highlights
Zinc is a catalytic element that is involved in modulating a large number of enzymes, and plays important biological and structural roles in many cellular events [1]
For the investigation of chelation mechanism, oligopeptides with spatially isolated binding sites have been used as promising models [6] since the affinity of chelating metal ions towards specific binding sites is largely determined by the sequence of the peptide structures [7]
Several reports have suggested that specific amino acid residues such as Glu, His and Asp significantly contribute to zinc chelation capacity of peptides [20]
Summary
Zinc is a catalytic element that is involved in modulating a large number of enzymes, and plays important biological and structural roles in many cellular events [1]. To overcome the problem arisen from the interaction of zinc-phytate, an approach that biologically associates zinc with phytate competitors has been suggested as a promising way [4]. An increasing number of zinc supplements, especially bioactive peptides, with the capability to promote and enhance zinc bioavailability, are being identified and characterized. Food-derived bioactive peptides generated from proteolysis of the primary structures of proteins can exhibit diverse bioactivities, such as metal chelation and enhancement of metal absorption in the gastrointestinal system [5]. For the investigation of chelation mechanism, oligopeptides with spatially isolated binding sites have been used as promising models [6] since the affinity of chelating metal ions towards specific binding sites is largely determined by the sequence of the peptide structures [7]
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