The reaction of a high-valent nonheme oxoiron(IV) intermediate with hydrogen peroxide.

Reactive oxygen species (ROS) are versatile small molecules that under normal homeostatic control are essential for physiological signaling, whereas an improper balance can lead to aging and age-related diseases. A main regulatory mechanism for the ROS hydrogen peroxide (H2O2) is associated with heme enzymes called catalases. These metalloenzymes dismutate two molecules of H2O2 via the proposed reaction pathways shown in Equations (1) and (2). Initial oxidation of the Fe resting state with H2O2 generates a high-valent oxoiron(IV) porphyrin p-cation radical, also known as compound I, [(PC)Fe=O], where P= porphyrinate dianion [Eq. (1)]. The reaction of compound I with a second molecule of H2O2 results in the return to the resting state of the enzyme with the release of water and dioxygen [Eq. (2)]. Considering the reactivity of compound I toward H2O2 in heme enzymes, a similar interaction with H2O2 has not been reported for oxoiron(IV) intermediates involved in the catalytic cycles of mononuclear nonheme iron enzymes.