Effect of zinc ion on peroxidase activity of serum in cow

In this study, for clarifying some possible mechanism of zinc toxicity, the effect of increasing amounts of Zn2+ ion on peroxidase activity was investigated in vitro in serum of cow. The H2O2-mediated oxidation of o-dianisidine was used to assess the peroxidase activity. Results show that after preincubation of serum with 0.2-20 mM Zn2+ concentration for 5 min, peroxidase activity was inhibited compared to the control and decreased rapidly with increasing metal concentrations. The enzyme was completely inhibited after 5 min preincubation in 30 mM Zn2+. When the preincubation of serum and Zn2+ was prolonged to 30 and 60 min, the enzymatic activity decreased more rapidly with increasing metal concentration. Extended exposure of the enzyme to lower concentrations of the metal brought about the same effect as shorter exposure to higher metal concentrations.