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 CaCl 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.