Purification and characterization of a novel calcium-biding decapeptide from Pacific cod (Gadus Macrocephalus) bone: Molecular properties and calcium chelating modes

The calcium-binding peptides were recognized as novel functional ingredients for improving calcium bioavailability. Pacific cod (Gadus Macrocephalus) bone gelatin hydrolysates (BGH) with considerable calcium binding activity (0.41 ± 0.08 μg/mg) were prepared and then separated by hydroxyapatite specific affinity column chromatography and reversed phase high performance liquid chromatography. A novel decapeptide was purified and identified as KGDPGLSPGK (designated Peptide-K, MW: 954.5 Da), which exhibited the highest calcium binding activity (2.53 ± 0.12 μg/mg) among BGH. The calcium-binding sites were investigated by circular dichroism (CD), Fourier transform infrared spectroscopy (FTIR), and mass spectrometry (MS). Results indicated that the carboxylate O atoms of Asp-3 and Lys-10 and the side chain amino N atom of Lys-10 in Peptide-K contributed to the calcium-chelating reaction. Possible chelating modes between Ca2+ and Peptide-K were constructed based on the obtained data. Results may contribute to a better understanding of the chelating process between Ca2+ and calcium-binding peptides.