Till Death Do Us Part: The Marriage of Autophagy and Apoptosis

Figure 3

Schematic illustration of the mechanism involved in reactive oxygen species (ROS) formation and elimination. Endogenous forms of ROS arise from NADPH oxidase (NOX) as well as the organelles shown. The cytosolic superoxide (O₂⁻) is converted into hydrogen peroxide (H₂O₂) by superoxide dismutase (SOD). H₂O₂ has three fates. It can be detoxified to water by glutathione peroxidase (GPX) peroxiredoxin (PRx), thioredoxin (TRX), and catalase (CAT). The reduced form of glutathione (GSH) promotes this reaction whereas oxidation to glutathione disulfide GSSH results in intracellular redox. H₂O₂ can be converted to the cytotoxic hydroxyl radical (OH⁻) via the Fenton reaction resulting in irreversible damage to lipids, proteins, and DNA. Lastly, H₂O₂ can also be used as a signaling molecule by oxidizing critical thiols within proteins to regulate numerous biological processes.