Summary
The calcium phosphate remaining after hydrazine deproteination of casein micelles isolated from bulk skim milk exhibits under the electron microscope a very fine and uniform granularity being formed by small subunits with a true diameter of approximately 2.5 nm. This material, which is about 10 percent by weight citrate, termed calcium phosphate citrate (CPC) complex, also contains Mg and Zn at molar ratios of 0.03 and 0.003 respectively. Radial distribution function (RDF) and infrared analyses show that CPC is a Mg-containing amorphous calcium phosphate (ACP) similar to synthetic and cytoplasmic ACP. Presence of CPC in casein micelles as an amorphous colloid bonded with phosphoproteins provides the means for storing in milk large amounts of Ca (16 mM) and Pi (10 mM) in a readily utilizable form but at a higher ion concentration than found in biological solutions.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Pyne, G.T., McGann, T.C.A.: The colloidal phosphate of milk. II. Influence of citrate. J. Dairy Res. 27: 9–17, 1960.
McGann, T.C.A., Pyne, G.T.: The colloidal phosphate of milk. III. Nature of its association with casein.
Richardson, T., McGann, T.C.A., Kearney, R.D.: Levels and location of adenosine 5′-triphosphate in bovine milk. J. Dairy Res.47: 91–96, 1980.
Lehninger, A.L.: Mitochondria and biological mineralization processes: An exploration. Horizons Biochem. Biophys.4: 1–30, 1977.
Betts, F., Posner, A.S.: A structural model for ACP. Trans. Amer. Cryst. Assoc.10: 73–84, (1974).
Termine, J.D., Eanes, E.D., Greenfield, D.J., Nylen, M.U.: Hydrazine-deproteinated bone mineral. Calc. Tiss. Res.12: 73–90, (1973).
Buchheim, W.: A comparison of the microstructure of dried milk products by freeze-fracturing powder suspensions in non-aqueous media. Scanning Electron Microsc. 111: 493–502, 1981.
Thomas, R.S., Greenwalt, J.W.: Micorincineration, electron microscopy, and electron diffraction of calcium phosphate-loaded mitochondria. J. Cell Biol.39: 55–57, 1968.
Hurley, L.S., Lonnerdal, B.: Zinc Binding in human milk: citrate versus Picolinate. Ntr. Revs.40: 65–71, 1982.
Brudevold, F., Steadman, L.T., Spinelli, M.A., Amdur, B.H., Gron, P.: A study of zinc in human teeth. Arch. Oral Biol.8:135–144, 1963.
Calhoun, N.R., Smith, Jr., J.C., Becker, K.L.: The role of zinc in bone metabolism. Clin. Orthop.103: 212–233, 1974.
Blumenthal, N.C., Betts, F., Posner, A.S.: Stabilization of amorphous calcium phosphate by Mg and ATP. Calcif. Tiss. Res.23:245–250, 1977.
Meyer, J.L., Angino, E.E.: The role of trace metals in calcium urolithiasis. Invest. Urol.14: 347–350, 1977.
Knoop, A.M., Frede, E., Precht, D.: Die submikroskopische struktur naturlicher und kunstlicher casein micellen. Milchwissenschaft.34: 129–131, 1979.
Brecevic, L.J. Furedi-Milhofer, H.: Precipitation of calcium phosphates from electrolyte solutions. V. The influence of citrate ions. Calcif. Tissue Int.28: 131–136, 1979.
Schmidt, D.G., Buchheim, W.: On the size of small protein particles determined by electron microscopy of unidirectionally shadowed freeze-etched preparations. J. Microsc.126: 347–351, 1982.
Robinson, R.A., Watson, M.L.: Crystal-collagen relationships in bone as observed in the electron microscope. III. Crystal and collagen morphology as a function of age. Ann. N.Y. Acad. Sci.60: 596–628, 1955.
Bonnuci, E.: Fine structure and histochemistry of "calcifying globules" in epiphyseal cartilage. Z. Zellforsch103: 192–217, 1970.
Knoop, A.M., Knoop, E., Wiechen, A.: Substructure of synthetic casein micelles. J. Dairy Res.46: 347–350, 1979.
Betts, F., Blumenthal, N.C., Posner, A.S., Becker, G.L., Lehninger, A.L.: Atomic structure of intracellular amorphous calcium deposits. Proc. Nat Acad. Sci.72: 2088–2090, 1975.
Posner, A.S.: Intramitochondrial storage of stable amorphous calcium phosphate. Ann. N.Y. Acad. Sci.307: 248–249, 1978.
Pyne, G.T.: Some aspects of the physical chemistry of the salts in milk. J. Dairy Res.29: 101–130, 1962.
Blumenthal, N.C., Betts, F., Posner, A.S.: Effect of carbonate and biological macromolecules on formation and properties of hydroxyapatite. Calcif. Tiss. Res. 18: 18–90, 1975.
Holt, C., Hasnain, S.S., Hukins, D.W.L. Structure of bovine milk calcium phosphate determined by x-ray absorption spectroscopy. Biochimica et Biophysica Acta,719: 299–303, 1982.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
McGann, T.C.A., Kearney, R.D., Buchheim, W. et al. Amorphous calcium phosphate in casein micelles of bovine milk. Calcif Tissue Int 35, 821–823 (1983). https://doi.org/10.1007/BF02405131
Issue Date:
DOI: https://doi.org/10.1007/BF02405131