Novel Peptide with a Specific Calcium-Binding Capacity from Whey Protein Hydrolysate and the Possible Chelating Mode

Abstract

A novel peptide with a specific calcium-binding capacity was isolated from whey protein hydrolysates. The isolation procedures included diethylaminoethyl (DEAE) anion-exchange chromatography, Sephadex G-25 gel filtration, and reversed-phase high-performance liquid chromatography (HPLC). A peptide with a molecular mass of 237.99 Da was identified by liquid chromatography-electrospray ionization/mass spectrometry (LC-ESI/MS), and its amino acid sequence was confirmed to be Gly-Tyr. The calcium-binding capacity of Gly-Tyr reached 75.38 μg/mg, increasing by 122% when compared to the hydrolysate complex. The chelating interaction mode between the Gly-Tyr and calcium ion was investigated, indicating that the major binding sites included the oxygen atom of the carbonyl group and nitrogen of the amino or imino group. The folding and structural modification of the peptide arose along with the addition of the calcium ion. The profile of (1)H nuclear magnetic resonance (NMR) spectroscopy demonstrated that the electron cloud density around the hydrogen nucleus in the peptide changed was caused by the calcium ion. The results of ζ potential showed that the Gly-Tyr-Ca chelate was a neutral molecule in which the calcium ion was surrounded by the specific binding sites of the peptide. Moreover, thermogravimetry-differential scanning calorimetry (TG-DSC) and calcium-releasing assay revealed that the Gly-Tyr-Ca chelate exerted excellent thermal stability and solubility in both acidic and basic conditions, which were beneficial to calcium absorption in the gastrointestinal tract of the human body and, therefore, improved its bioavailability. These findings further the progress in the research of whey protein, suggesting the potential in making peptide-calcium chelate as a dietary supplement.

A possible mechanism for enhancing the antioxidant activity by pulsed electric field on pine nut peptide Glutamine‐Tryptophan‐Phenylalanine‐Histidine

“…A research found that the α‐helix in the secondary structure of the lysozyme was destroyed and then the absorption intensity of UV absorption spectrum decreased obviously (Zhao & Yang, ). A similar research has reported that the UV absorption of the peptide was increased, and its spatial structure was changed after the chelation of Gly‐Tyr with metal ions (Zhao et al, ). The absorption peak of QWFH at 250–300 nm, the characteristic absorption of conjugated structure (such as benzene) in the residues of Trp and Phe, was detected, indicating that the microenvironment of the amino acid (Trp and Phe) residues was affected.…”

“…and its spatial structure was changed after the chelation of Gly-Tyr with metal ions (Zhao et al, 2014). The absorption peak of QWFH at 250-300 nm, the characteristic absorption of conjugated structure (such as benzene) in the residues of Trp and Phe, was detected, indicating that the microenvironment of the amino acid (Trp and Phe) residues was affected.…”

Optimised condition for preparing sea cucumber ovum hydrolysate–calcium complex and its structural analysis

“…It was also observed that the band of 1451.23 cm −1 in the spectrum of the SCOHs moved to a lower frequency at 1441.91 cm −1 , which could be caused by the vibration of carboxylate group after the chelation. Besides, several absorption peaks for the SCOHs–Ca in the range 800–500 cm −1 arise from the vibration of the C–H and N–H bonds, and these bands disappeared in the SCOHs spectrum (Zhao et al ., ). These changes in bands indicated that the calcium binds to the SCOHs primarily via interactions with carboxyl oxygen and amino nitrogen atoms, which were similar to the peptide–calcium complexes derived from wheat germ protein hydrolysates (Liu et al ., ).…”

Emerging trends in nutraceutical applications of whey protein and its derivatives

“…A novel peptide GlyTyr with a specific calcium-binding capacity was isolated from whey protein hydrolysate. The chelating mechanism of the peptide was investigated and the major binding sites were found to be the oxygen atom of the carbonyl group and nitrogen of the amino or imino group (Zhao et al 2014). This peptide might boost calcium absorption in the gastrointestinal tract and developing the peptide-calcium chelate as a supplement for enhanced calcium bioavailability seems promising.…”