Casein calcium-binding peptides: Preparation, characterization, and promotion of calcium uptake in Caco-2 cell monolayers

In this study, casein calcium-binding peptides were isolated from casein hydrolysate using calcium-peptide binding properties and their banding properties were characterized. Subsequently, the promoted calcium absorption abilities of casein calcium-binding peptides in the Caco-2 cells monolayers were investigated. Amino acid composition analysis showed that casein calcium-binding peptide-calcium chelate are rich in Glu, Ser, and Asp, with a significant increase in proportion compared to the casein hydrolysate. Molecular weight analysis showed that approximately 90 % of the casein calcium-binding peptides are oligopeptides. Thirty-seven peptide sequences were identified by mass spectrometry, and the presence, quantity, and position of some specific amino acid residues were found to correlate with calcium-binding ability. Additionally, calcium-peptide binding properties were characterized by using Ultraviolet-Visible spectroscopy, Fourier transform infrared spectroscopy, and scanning electron microscopy, which indicated that calcium ions were mainly chelated with the amino nitrogen atoms and oxygen atoms on the carboxyl group of casein calcium-binding peptides, thus forming chelate with porous microstructures. Compared with the control group, the casein calcium-binding peptides treatment group showed a significant increase in calcium transport at 30, 60, 120 and 180 min, respectively, by 44.25 %, 31.21 %, 20.67 % and 24.08 %. Therefore, casein calcium-binding peptides are expected to be used as dietary calcium supplements.