Ca2+-Binding Glycoprotein in Avian Bone Induced by Estrogen

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Abstract
The discovery in calcifying cartilage of a glycoprotein, endowed with high calcium affinity and alkaline phosphatase activity, has prompted the investigation of the presence of this compound in other calcified tissues. From medullary bone, a tissue which is highly mineralized under estrogen stimulus, a glycoprotein has been extracted which had the properties described. Besides the high calcium affinity (Kd = 10−7M), this protein shows phosphatase activity and rate of hydrolysis of ATP, GTP and pyrophosphate was measured. Analysis of the chemical composition of the matrix of the medullary bone indicates that proteoglycans are present in large amounls. The calcium binding glycoprotein appears to be a compound present in different calcified tissues.