The effect of vitamin D upon bone mineralization of Ca45 and Sr89 as chlorides and as phosphopeptides.

An organic compound containing 5.86 per cent phosphorus and 11.9 per cent nitrogen was isolated (1) from the tryptic digest of bovine milk casein. Further study (2) suggested that, since serine was the only hydroxyamino acid in the compound, it appeared likely that phosphoric acid was bound to the hydroxy group of this amino acid. A serine phosphoric acid was prepared directly from casein (3) and phosphoserylglutamic acid was isolated (4) from phosphopeptones. A phosphopeptone was also isolated (5) from bovine milk casein. The first detailed description of a suitable procedure for preparation of phosphopeptone was outlined by Rimington (6). A modification of this method (6, 7) was made by Mellander (S), who obtained a concentrate of calcium phosphopeptones from bovine and human milk casein. A water-soluble organic factor (9) which was found in casein and which influenced bone mineralization in chicks has been reported. The influence of this factor could be destroyed by dialysis or upon hydrolysis with Rhozyme P-11, a proteolytic enzyme. The following experiments were designed to study the biological relationship of vitamin D to utilization of the radionuclides Ca45 and Srsg in the form of Ca45 or Srsg phosphopeptides by chicks and rats.