Reduction of Hydrogen Peroxide by Human Mitochondrial Amidoxime Reducing Component Enzymes

The mitochondrial amidoxime reducing component (mARC) is a human molybdoenzyme known to catalyze the reduction of various N-oxygenated substrates. The physiological function of mARC enzymes, however, remains unknown. In this study, we examine the reduction of hydrogen peroxide (H(2)O(2)) by the human mARC1 and mARC2 enzymes. Furthermore, we demonstrate an increased sensitivity toward H(2)O(2) for HEK-293T cells with an MTARC1 knockout, which implies a role of mARC enzymes in the cellular response to oxidative stress. H(2)O(2) is a reactive oxygen species (ROS) formed in all living cells involved in many physiological processes. Furthermore, H(2)O(2) constitutes the first mARC substrate without a nitrogen–oxygen bond, implying that mARC enzymes may have a substrate spectrum going beyond the previously examined N-oxygenated compounds.