Catalytic peroxidase-like activity of an iron-containing crystallite isolated from ferritin in aqueous solution and reversed micelles of aerosol OT in heptane

A comparative study of the catalytic activity of an iron-containing cluster (Fe3+-crystailite) from horse spleen ferritin and of whole ferritin in the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by hydrogen peroxide in acetate buffer containing 10% DMFA and in reversed micelles of Aerosol QT (AOT) in heptane was performed. In an aqueous medium, the catalytic activity of ferritin is much higher than that of the Fe3+-cluster. This confirms the extremely important role of apoferritin in the peroxidase function of this biocatalyst. In the AOT micelles in heptane. the activities of Fe3+-crystallite and whole ferritin are comparable and, to a large extent, determined by the hydration degree of micelles W-0. The dependences of the initial rates of the oxidation of TMB on W-0 have one maximum at W-0 35 for Fe3+-crystallite and three maxima at W-0 10, 20, and 30 for whole ferritin. The role of Fe3+-crystallite in coordination and activation of H2O2 and the possible role of apoferritin in binding and orientation of TMB near the active Fe3+-containing sites of ferritin are discussed.