Studies on Cytochrome c Peroxidase

Apoproteins of cytochrome c peroxidase, horseradish peroxidase, and sperm whale myoglobin were recombined with manganese complexes of proto-, hemato-, meso-, and deuteroporphyrins to form manganese porphyrin-protein complexes. These complexes were purified by column chromatography. All the manganese porphyrin-containing cytochrome c peroxidases were crystallized. Light absorption maxima of manganese porphyrins were shifted to longer wave lengths upon binding to these apoproteins. Light absorption maxima of manganese porphyrin-protein complexes and their derivatives were shifted to shorter wave lengths to the extent of 1 to 10 rnp in the order of proto-, hemato-, meso-, and deuteroderivatives. Manganese-porphyrins and their protein complexes exhibited no appreciable electron paramagnetic resonance absorption at 196”. Manganese porphyrin-containing peroxidases reacted with hydroperoxides to form peroxide compounds and catalyzed the peroxidatic oxidation of ferrocytochrome c, ferrocyanide, and ascorbate at reasonable rates. The peroxide compounds of manganese porphyrincontaining horseradish peroxidases were highly stable and appeared to be a manganese (IV) derivative. The peroxide compounds of manganese porphyrin-containing cytochrome c peroxidases were less stable and retained 2 oxidizing equivalents per mole of the enzyme. However, the chemical nature of the compound was not established. Manganese porphyrin-containing myoglobin neither formed peroxide compounds nor exhibited peroxidase activity under comparable conditions. These myoglobin derivatives and their dithionite-reduced compounds did not form complexes with oxygen and carbon monoxide.