A novel zinc-binding peptide identified from tilapia (Oreochromis niloticus) skin collagen and transport pathway across Caco-2 monolayers

Tilapia (Oreochromis niloticus) skin collagen hydrolysates (TSCHs) were obtained using Alcalase, Trypsin, and Protamex. Our results indicated that enzyme type, degree of hydrolysis, and molecular weight distribution significantly affected the zinc-binding capacity of TSCHs. Five peptides were isolated and purified via immobilized metal affinity chromatography and reversed-phase high performance liquid chromatography. Their amino acid sequences were LGPY, GFLGSP, FHGLR, LGYPGPKGSP, and LRGLPGSVGEQ. Of these, the peptide GFLGSP exhibited the highest zinc-binding capacity. Fourier transform infrared spectroscopy demonstrated that the zinc-binding sites were located at the nitrogen atom of the amino group and the oxygen atom of the carboxyl group of the peptide GFLGSP. Scanning electron microscopy revealed that the surface morphology of GFLGSP was changed after adding zinc. Furthermore, GFLGSP had strong stability during simulated gastrointestinal digestion. Caco-2 cell monolayer experiments indicated that GFLGSP can be transported and that the paracellular pathway via tight junctions was the transport pathway.