Binding of calcium by proteoglycansin vitro |
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Authors: | Dominic D Dziewiatkowski |
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Institution: | (1) The Dental Research Institute and Department of Oral Biology, School of Dentistry, The University of Michigan, 48109-1078 Ann Arbor, Michigan MI |
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Abstract: | Summary Proteoglycans from bovine nasal septa or the Swarm rat chondrosarcoma, as potassium salts, effectively inhibit the precipitation
of tricalcium phosphatein vitro at pH 7.8. The same preparations, and many other similar preparations, however, do not site bind calcium, as assessed with
a calcium ion specific electrode. However, after treatment of aggregate preparations of proteoglycans with EDTA, the preparations
can site bind calcium. The amount thus bound is approximately equal to one-half the sum of the equivalents of the ester sulfate
and the uronic acid carboxyl groups in the preparations. This latter observation suggested the possibility that the supposed
potassium salts of the proteoglycans had, in the course of preparation, acquired calcium and held onto it strongly. In checking
this possibility, using neutron activation analysis, it was found that some of the preparations do contain small amounts of
calcium but these amounts are insufficient to saturate the binding sites potentially available to this end. In view of the
above observations, it is suggested that the proteoglycans inhibit the formation of calcium phosphate precipitatesin vitro not because the calcium is site bound but because the calcium ions are territorially bound. |
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Keywords: | Proteoglycans Calcium-binding Endochondral ossification |
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