Purification, Identification, Chelation Mechanism, and Calcium Absorption Activity of a Novel Calcium-Binding Peptide from Peanut (Arachis hypogaea) Protein Hydrolysate

Abstract

A novel calcium-binding peptide was purified from peanut protein hydrolysate using gel filtration chromatography and identified using HPLC-MS/MS. Its amino acid sequence was determined as Phe-Pro-Pro-Asp-Val-Ala (FPPDVA, named as FA6) with the calcium-binding capacity of 15.67 ± 0.39 mg/g. Then, the calcium chelating characteristics of FPPDVA were investigated using ultraviolet−visible absorption spectroscopy, fluorescence spectroscopy, Fourier transform infrared spectroscopy, particle size, and zeta potential. The results showed that FPPDVA interacted with calcium ions, the chelation of calcium ions induced FPPDVA to fold and form a denser structure, the calcium-binding sites may mainly involve oxygen atoms from the carboxyl residues of Asp and Ala, and Phe possessed contact energy and carbonyl residues of Val. Microstructure analysis showed that FPPDVA-calcium chelate exhibited a regularly ordered and tightly aggregated sheets or block structures. Additionally, FPPDVAcalcium chelate had good gastrointestinal digestive stability and thermal stability. The results of everted rat intestinal sac and Caco-2 cell monolayer experiments showed that FPPDVA-calcium chelate could promote calcium absorption and transport through the Cav1.3 and TRPV6 calcium channels. These data suggest that FPPDVA-calcium chelate possesses the potential to be developed and applied as calcium supplement.

A critical review of a typical research system for food‐derived metal‐chelating peptides: Production, characterization, identification, digestion, and absorption

“…Moreover, the significance of the electronic clouds generated in the receptors and donors has been demonstrated in the chelation of peanut protein peptides (FPPDVA) and calcium (Figure 3a). Furthermore, according to a comparison of the frontier molecular orbital analyses of peptides and peptide–calcium complexes, the oxygen atoms in the carboxyl group (Asp and Ala) and Phe were confirmed to possess contact energies, whereas the oxygen atom of the carbonyl group in Val might be the main potential binding site (Wang, Zhang, et al., 2023). Similarly, charge‐type interactions were discovered between iron ions and the carboxyl groups of acidic amino acids (Fan, Ge, et al., 2023), which was in accordance with the theory stating that these acidic amino acids (negatively charged) could offer a significant platform for supporting charge interactions with divalent metal ions.…”

“…Peptides generally connect with metal ions via metal receptors, whereas ions and amino groups mainly interact via metal donors, and ions and carboxyl groups primarily interact via metal charges (Wang et al., 2021). When MCPs bind metal ions, the electron clouds of the ligands change because of the high steric hindrances and contact energies of amino acid residues, which leads to further speculations on the chelation type, distance, and docking energy (Wang, Zhang, et al., 2023). The binding of iron ions to peanut peptides was predicted and modeled using molecular docking techniques, and the carboxyl groups provided by acidic amino acids (including glutamic acid) played crucial roles in this binding (binding distances ranged from 2.0 to 2.8 Å) (Fan, Wang, et al., 2023).…”

“…The binding of iron ions to peanut peptides was predicted and modeled using F I G U R E 3 Molecular dockings of metal-chelating peptides (MCPs) and metal ions. (a) FA6 (the peanut protein hydrolysate FPPDVA) (above) and FA6-calcium complex (below) (Wang, Zhang, et al, 2023). (b) Three-dimensional (3D) structure of IEELEEELEAER-calcium (Mytilus edulis protein hydrolysate) complex (above) and interaction between Glu2 and calcium (below) (Xu, Zhu, et al, 2022).…”

“…This is because the hydrogen ions offered by the acidic environment can compete with metal ions from the chelating sites, resulting in dissociations of these ions from the MCP–metal complexes and the presence of metals in free forms. Consequently, the ions are rapidly converted into metal salt precipitates, which may lead to relatively inferior ion retention in the alkaline environment of the digestive tract (Wang, Zhang, et al., 2023; Zhang, Ding, et al., 2021). Thus, to improve the availabilities of metals under these conditions, numerous alternatives, including liposomes, polymer nanoparticles, polysaccharides, hydrogels, and self‐emulsifying delivery systems, to protect minerals have gradually evolved (Zhang et al., 2022).…”

Glycated Walnut Meal Peptide–Calcium Chelates: Preparation, Characterization, and Stability

“…After chelating with calcium, the surface of the WMPHs-COS-Ca became loose with irregular depressions, transitioning from flakes to numerous granular aggregates, which was attributed to the coordination between the WMPHs-COS and calcium ions. The carboxyl and amino groups combine with Ca 2+ to create a "bridging effect", resulting in alterations in the internal structure and the formation of a compact chelate structure [57]. The impact of temperature on protein processing is significant.…”