Phosphopeptides from a Tryptic Hydrolysate of Human Casein.

Abstract
Phosphopeptides have been isolated by anion exchange chromatography from a tryptic hydrolysate of human casein. The homogeneity of the phosphopeptide with the highest phosphorus content has been demonstrated and its amino acid composition and terminal amino acid residues determined. It contains 19 amino acid residues and 5 phosphate groups and appears to have the composition Arg[Thr2, Ser5, Glu5, Ileu3, Leu, (PO4)5]Tyr, Lys one of the glutamic acid residues possibly being in amide form.