Calcium-dependent polymerization of human serum amyloid P component is inhibited by heparin and dextran sulfate

The calcium-dependent polymerization of human serum amyloid P component (SAP) was spectrophotometrically monitored in 0.15 M NaCl at pH 7.5. The rate of the polymerization depended on the concentrations of SAP and Ca2+. It was shown for the first time that the calcium-dependent polymerization of SAP was inhibited by some sulfated polysaccharides. Most potent inhibitors were heparin and high molecular weight dextran sulfate of Mr 1.0.10(6). The inhibitory activity of glycosaminoglycans is accordant to their binding affinity for SAP, which was reported previously (Hamazaki, H. (1987) J. Biol. Chem. 262, 1456-1460). The polymerized SAP was reversibly dissociated by heparin and high molecular weight dextran sulfate. The results suggest that heparin and high molecular weight dextran sulfate may be a useful dissociating agent of polymerized SAP in amyloid deposits.