Study on the Calcium Transport-Promoting Property and Mechanism of the Peptide–Calcium Complex DEEENDQVK–Ca Based on a Caco-2 Monolayer Model

Peptide–calcium complexes exhibit promise as calcium supplements due to their enhanced bioavailability. Phosvitin nonapeptide DEEENDQVK (DK) possesses a high calcium-binding capability. This study investigated the calcium transport-promoting properties of DK and DEEENDQVK–calcium complex (DK–Ca) using a Caco-2 monolayer model. Both DK and DK–Ca concentration-dependently promoted calcium transport, and compared with the CaCl2 control, enhanced calcium transport by 1.07-fold and 1.83-fold, respectively. The calcium transport channels and mechanisms of DK and DK–Ca were also investigated using transfer channel regulators, real-time quantitative polymerase chain reaction, and molecular docking. The results showed that DK–Ca primarily promoted calcium transport through the TRPV6 channel, with supplementary contributions from paracellular and endocytosis channels, while DK did not rely on the endocytosis channel. DK and DK–Ca promoted calcium transport by upregulating TRPV6, calbindin-D9k, PMCA1b, and claudin-2 mRNA expression. DK–Ca exhibited a higher binding affinity for TRPV6 (−10.0 kcal/mol) compared to DK (−5.5 kcal/mol). DK–Ca primarily binds TRPV6′s extracellular exposed cavity through hydrogen bonds and hydrophobic interactions, increasing the local calcium concentration at the channel entrance to promote calcium absorption. This study provides cellular-level mechanistic clues for the potential effects of DK–Ca as a calcium supplement.