How do cells regulate ROS levels?

Cellular ROS sensing and metabolism are both tightly regulated by various proteins involved in the redox mechanism. More specifically, ROS are maintained via tight control of their sources and scavenging. Levels of H2O2 are regulated by different scavenging or antioxidant enzymes. As an example, catalase dismutates H202 to H20 and oxygen, or it reduces H2O2 to H20 via oxidizing hydrogen-donating compounds. Cells also possess non-enzymatic molecules that scavenge and neutralize ROS, such as glutathione and vitamins C and E. Cells also use repair mechanisms to counteract oxidative damage to cellular components. DNA repair mechanisms correct DNA damage induced by ROS to prevent mutations. Protein repair mechanisms repair oxidatively damaged proteins through processes like chaperone-mediated refolding. Heat shock proteins act as molecular chaperones that assist in the refolding of denatured or oxidatively damaged proteins.