Analysis of function of phosphopeptides from milk and egg phosphoproteins

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Phosphopeptides were separated from the tryptic hydrolyzates of bovine αィイD2s1ィエD2-casein, bovine β-casein and egg white riboflavin-binding protein (RfBP). The inhibitory activity for calcium phosphate of these phosphopeptides was in the order of β-casein-4P (f1-25) > αィイD2s1ィエD2-casein-5P (f59-79) and RfBP (f182-204), suggesting that there was an optimum number of phosphate groups. Subsequently, the inhibitory activity of human β-casein phosphopeptides having 1-5 phosphate groups were examined. Human β-casein phosphopeptides having 4 and 5 phosphate groups showed the highest inhibitory activity.The calcium absorption rate determined by the radioisotope method was in the order of casein diet > RfBP diet >soy protein diet. The soluble calcium percent in the small intestine was in the order of RfBP diet > casein diet > soy protein diet. These results suggested that phosphoprotein having higher calcium phosphate-solubilizing ability did not always show higher calcium absorption rate, and that there was an optimum number of phosphate groups in the calcium absorption-stimulating ability.The method for the preparation micellar calcium phosphate (MCP)-phosphopeptides complex was established. The excellent bioavailability of MCP-phosphopeptides in rats was shown.