Oxidoreductase activities of polyclonal IgGs from the sera of Wistar rats are better activated by combinations of different metal ions

It was shown that IgGs purified from the sera of healthy Wistar rats contain several different bound Me 2+ ions and oxidize 3,3′‐diaminobenzidine through a H 2 O 2 ‐dependent peroxidase and H 2 O 2 ‐independent oxidoreductase activity. IgGs have lost these activities after removing the internal metal ions by dialysis against EDTA. External Cu 2+ or Fe 2+ activated significantly both activities of non‐dialysed IgGs containing different internal metals (Fe ≥ Pb ≥ Zn ≥ Cu ≥ Al ≥ Ca ≥ Ni ≥ Mn > Co ≥ Mg) showing pronounced biphasic dependencies corresponding to ∼0.1–2 and ∼2–5 mM of Me 2+ , while the curves for Mn 2+ were nearly linear. Cu 2+ alone significantly stimulated both the peroxidase and oxidoreductase activities of dialysed IgGs only at high concentration (≥ 2 mM), while Mn 2+ weakly activated peroxidase activity at concentration >3 mM but was active in the oxidoreductase oxidation at a low concentration (<1 mM). Fe 2+ ‐dependent peroxidase activity of dialysed IgGs was observed at 0.1–5 mM, but Fe 2+ was completely inactive in the oxidoreductase reaction. Mg 2+ , Ca 2+ , Zn 2+ , Al 2+ and especially Co 2+ and Ni 2+ were not able to activate dialysed IgGs, but slightly activated non‐dialysed IgGs. The use of the combinations of Cu 2+  + Mn 2+ , Cu 2+  + Zn 2+ , Fe 2+  + Mn 2+ , Fe 2+  + Zn 2+ led to a conversion of the biphasic curves to hyperbolic ones and in parallel to a significant increase in the activity as compared with Cu 2+ , Fe 2+ or Mn 2+ ions taken separately; the rates of the oxidation reactions, catalysed by non‐dialysed and dialysed IgGs, became comparable. Mg 2+ , Co 2+ and Ni 2+ markedly activated the Cu 2+ ‐dependent oxidation reactions catalysed by dialysed IgGs, while Ca 2+ inhibited these reactions. A possible role of the second metal in the oxidation reactions is discussed. Copyright © 2008 John Wiley & Sons, Ltd.