1.14.99.1 Fe2+ ferric heme enzyme 1.14.99.1 Fe3+ - 1.14.99.1 Iron possibly contains heme and non-heme iron 1.14.99.1 Iron each subunit contains a molecule of Fe3+-protoporphyrin IX noncovalently attached to the enzyme, the heme group is essential for both enzyme activities, the cofactor is released by induction of inhibitor nitroarachidonic acid 1.14.99.1 Mn3+ substitution of ferric heme by MnIII protoporphyrin IX greatly diminishes the peroxidase activity, but has little effect on the cyclooxygenase activity