Isolation, characterization, and molecular docking analyses of novel calcium-chelating peptide from soy yogurt and the study of its calcium chelation Mechanism.

BACKGROUND
Calcium is an essential dietary mineral nutrient for humans. Digestive instability limits the bioavailability of calcium ions. Peptide-calcium chelate has been proven to exciting higher calcium absorption than amino acid-calcium chelate, organic and inorganic calcium. Soy yogurt, which is produced via liquid-state fermentation using lactic acid bacteria, has a high amount of bioavailable calcium. In this study, a novel peptide with high calcium-binding affinity was purified and identified from soy yogurt. Then the binding mechanism of peptide and calcium was analyzed by bioinformatics and spectral analysis. Furthermore, to investigate the effect of the novel peptide on gastrointestinal stability by the Caco-2 cell model, and calcium bioavailability in vivo by the zebrafish model.


RESULTS
The results showed that a novel peptide was purified and identified as DEDEQIPSHPPR(CBP). Calcium ions probably coordinate with Glu-2 and Glu-4 carboxyl groups via salt bridges and interact with Asp-1, Asp-3, and Arg-12 in CBP via charge pairing. The calcium-binding activity of the CBP was 36.64 ± 0.04 mg/g. Fourier transform infrared spectroscopy (FTIR) spectra showed that calcium spontaneously bound to the amino group nitrogen and oxygen atoms of the carboxyl group. The binding mode is either "bidentate or unidentate" depending on the circumstances. More importantly, the CBP peptide substantially increased the bone mass in a zebrafish osteoporosis model.


CONCLUSION
The more glutamic acid and aspartic acid, the high the calcium affinity with peptide. Soy yogurt-derived peptides can be used as carriers of calcium ions throughout the gastrointestinal tract (GIT), which may be clinically useful for osteoporosis therapy. This article is protected by copyright. All rights reserved.