Phosphorylation modification of tilapia skin gelatin hydrolysate and identification and characterization of calcium-binding peptides

In present study, complex protease was utilized to prepare tilapia skin gelatin hydrolysate (TSGH), and the phosphorylation conditions of TSGH were optimized using calcium-binding capacity. The phosphorylation degree of TSGH under the optimal conditions was 0.55%. The calcium-binding capacities of TSGH and phosphorylated TSGH were 44.21 and 62.87 µg/mg, respectively. Phosphorylation remarkably improved the calcium-binding capacity of TSGH. Forty-four peptides and 14 phosphopeptides were identified in phosphorylated TSGH, and SGPAGPK and its phosphopeptide, ( p )SGPAGPK, were screened. The calcium chelates of SGPAGPK and ( p )SGPAGPK were examined using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and mass spectrometry (MS). Phosphorylation of SGPAGPK effectively increased its calcium-binding capacity. SEM results indicated that SGPAGPK-Ca and ( p )SGPAGPK-Ca were formed as new compounds. FTIR and MS results indicated that the carboxyl and phosphate groups of Ser and the amino group of Lys may be the calcium chelation sites.