A novel β-casein peptide‑zinc chelate with enhanced zinc transport capacity: Preparation, chelation mechanism, and in vitro stability.

Zinc-chelating peptides have attracted attention because of their high bioavailability. In this study, β-casein peptide‑zinc chelates (β-CNP-Zn) were synthesized from β-casein, and their chelation mechanism, stability, and zinc transport properties were investigated. The results indicate that under alkaline protease hydrolysis, the maximum zinc chelation rate reached 53.7%. Glu and Asp residues in β-casein peptide were identified as the primary chelating amino acids, with carboxyl, carbonyl, and amino groups serving as the core zinc-binding sites. β-CNP-Zn exhibited good alkaline stability (74.60 ± 0.67%) and intestinal digestion stability (60.37 ± 0.65%). In Caco-2 cells, zinc transport rate of β-CNP-Zn was 1.48 times that of ZnSO4; inhibitor experiments suggest that the paracellular and endocytic pathways may be involved in its transport. LC-MS/MS identified 8 potential zinc-chelating peptides. Molecular docking indicated that stable chelation likely involves both carboxyl and carbonyl oxygen atoms. These findings suggest that β-CNP-Zn has potential as a novel zinc supplement.