Purification of a Novel Oligophosphopeptide with High Calcium Binding Activity from Carp Egg Hydrolysate

Abstract

In this paper, we determined appropriate degree of dephosphorization of carp eggs before trypsin hydrolysis according to the degree of hydrolysis and calcium binding activity, and purified a novel oligophosphopeptide with high calcium binding activity from carp eggs hydrolysate. The results showed that dephosphorization treatment can significantly increase the degree of hydrolysis (p < 0.05). However, hydrolysate of DP2 with 30.39% degree of dephosphorization owned the strongest calcium binding ability of 0.67 mmol/g-protein, and excessive dephosphorization was disadvantageous. After ultrafiltration, 88.73% content of hydrolysates was the fraction U1 with MW < 3 kDa which showed better ability to bind calcium. After hydroxyapatite chromatography, H3 eluted with the maximum concentration of phosphate buffer (400 mM) exhibited the highest calcium binding ability of 6.63 mmol/g-protein. Amino acid content analysis showed that the Ser content of H3 is about 2.5 times more than that of U1 but the contents of Thr and Tyr are almost identical. Further purification using size exclusion chromatography and high-performance liquid chromatography, an oligophosphopeptide with high calcium binding ability (7.85 mmol/g-protein) was obtained. Its sequence was identified as (pS)-S-(pS)-A-F-(pS)-(pS)-E-L-A-R through ESI-QTOF tandem mass analysis. It is possible to provide utilization of fish eggs as a novel calcium nutraceutical additive in food industry.