Protective action of blood ceruloplasmin obtained from normal individuals on red blood cells compared with that from patients with Wilson's disease.

A ceruloplasmin-like protein (pathological CP, p-CP) was isolated from the serum of patients with Wilson's disease whose antigenic determinant was identical to that of ceruloplasmin (CP) obtained from the blood of normal individuals. Because the protective action of CP involves its interaction with receptors on red blood cells (RBC), the binding of CP and p-CP to the RBC from normal individuals and to those from patients with Wilson's disease (p-RBC) was investigated. The number of binding sites for CP on both types of RBC was significantly lower than that for p-CP. The dissociation constants for CP-RBC and CP-p-RBC complexes were very similar (1.15 and 1.37 nM, respectively), as were those for the complexes of p-CP with RBC and p-RBC (11.1 and 11.8 nM, respectively), but the binding constants for p-CP with RBC of both types were ten times higher than the CP binding constants. The ability of CP to prevent Cu(2+)-induced lysis of RBC was significantly higher than that of p-CP. The protective action of CP and p-CP during RBC lysis in two Fe(2+)-containing systems did not correlate with their oxidative and ferroxidase activities. On the contrary, the protective effect of p-CP, which had significantly lower oxidase activity and no ferroxidase activity, was greater than that of CP.