Enzymatic properties of the Ca2+-binding glycoprotein isolated from preosseous cartilage.
The Ca2+-binding glycoprotein isolated from preosseous cartilage shows also alkaline phosphatase activity. The purification procedure indicates that the enzyme is inhibited in crude extract and conceivably in the intact tissue; the activity may be controlled by the proteoglycans present in the matrix. Other substrates are hydrolyzed by the purified enzyme in addition to p-nitrophenylphosphate; the highest specific activity was measured with ATP and pyrophosphate (PPi) at pH 7.5 and 9.0 Mg2+ induces an activation of ATP and PPi hydrolysis; Ca2+ activates hydrolysis of ATP but inhibits that of PPi. The glycoprotein shows also transphosphorylase activity, L-serine being the best phosphate acceptor. The release or transfer of Pi catalyzed by the glycoprotein can be an important step in calcium phosphate precipitation.
D000469:Alkaline Phosphatase / Q000378:metabolism*; D000818:Animals; D002113:Calcification, Physiologic; D002118:Calcium / Q000494:pharmacology; D002135:Calcium-Binding Proteins / Q000302:isolation & purification / Q000502:physiology*; D002356:Cartilage / Q000032:analysis / Q000201:enzymology*; D002417:Cattle; D006023:Glycoproteins / Q000302:isolation & purification / Q000502:physiology*; D008274:Magnesium / Q000494:pharmacology
D002135:Calcium-Binding Proteins; D006023:Glycoproteins; D000469:Alkaline Phosphatase; D008274:Magnesium; D002118:Calcium