Identification of novel calcium-absorption promoting peptides from lactopontin gastrointestinal digests and investigation of their intestinal calcium transport mechanism.

Abstract

Lactopontin (L-OPN), a milk-derived active protein vital for the growth of infants and young children, was studied for the calcium absorption-promoting activity and mechanism of its gastrointestinal digestive products. An in vitro dynamic infant digestive system simulated L-OPN digestion; the products were separated via desalting, ultrafiltration and HPLC to screen high calcium-chelating peptides. MS analysis revealed dominant low-molecular-weight peptides with acidic amino acids and serine phosphorylation. Molecular docking identified four high-affinity peptides: SELS(+79.97)KELTPK, KLS(+79.97)QEFH, HSDESDEVDF, PTDIPTIA, with Glu and Asp as key Ca2+-binding residues. In the Caco-2 model, their calcium transport rose by 83.55%, 95.44%, 71.53% and 81.62% vs. CaCl2 group, with lower intracellular calcium retention (accelerated Ca2+ efflux). MS confirmed KLS(+79.97)QEFH's intact intestinal absorption via stable calcium-chelating structure. This study clarifies L-OPN peptide's core calcium absorption mechanism, providing a scientific basis for understanding L-OPN's biological role and developing infant nutritional products.