Preparation and amino acid composition of enzymically dephosphorylated casein

Abstract

The preparation from ox spleen of a phosphoprotein phosphatase free from proteolytic activity and suitable as a dephosphorylating agent for casein is described. The preparation and some properties of dephosphorylated casein are described. In the preparation of the protein, advantage was taken of the insolubility of the dephosphorylated casein at pH 6.0, which is also the optimum pH for the enzymic dephosphoryla-tion. Acid-soluble N formed during enzymic dephosphorylation of casein was determined and the nature of the nitrogenous product investigated by paper chromatography. Dephosphorylated casein was analyzed for amino acids. Comparison of the values with those for casein shows that the amino acid composition of casein and its dephosphorylated product are about the same. During enzymic dephosphorylation of casein the protein remains relatively intact; the changes, if any, brought about by this treatment are not of a drastic nature. The relative merits of alkali and enzymic dephosphorylation methods are discussed.