[Identification of 2 phosphorylated amino acids in chicken bone phosphoproteins]

Phosphoproteins of Chicken bone have been extracted by 0.5 M EDTA pH 7.5. Their amino acid composition was similar to that of phosphoproteins of other calcified tissues. The crude EDTA extract contained 80 to 90% proteins, only 70% of the total organic phosphorus was bound to the proteins. We have studied and identified two phosphorylated components. o-phosphoserine and o-phosphothreonine have been identified by amino acid analysis at pH 1.7 from a partial acid hydrolysate, and confirmed by the liberation of the parent amino acids after total hydrolysis. In addition, phosphorus was found equimolecular to both of them. The presence of these phosphorylated groups is important for an understanding of the role of these proteins in the mechanism of mineralization.