<s>[INST] context: ROS are synthesized the NADPH oxidase (phagocyte oxidase) pathway and are released from neutrophils and macrophages that are activated by microbes, immune complexes, cytokines, and a variety of other inflammatory stimuli. NADPH oxidase also called respiratory burst oxidase When the ROS are produced within lysosomes they function to destroy phagocytosed microbes and necrotic cells Catalase, superoxide dismutase and glutathione peroxidase are free radical scavengers that prevent oxygen-mediated injury The NADPH oxidase complex is dormant under normal circumstances, but is activated to assemble in the membranes during respiratory burst The activated NADPH oxidase generates superoxide which has roles in animal immune response and plant signalling. Superoxide can be produced in phagosomeswhich have ingested bacteria and fungi or it can be produced outside of the cell. Superoxide kills bacteria and fungi by mechanisms that are not yet fully understood.It is presumed that superoxide kills bacteria directly, as the virulence of many pathogens is dramatically attenuated when their superoxide dismutase (SOD) genes are deleted. However, superoxide can also spontaneously form hydrogen peroxide that undergoes fuher reactions to generate other (ROS) like hydrochlorus acid (the reactive agent in bleach). It may also inactivate critical metabolic enzymes, initiate lipid peroxidation, damage iron sulphate clustersand liberate redox-active iron, which allows the generation of indiscriminate oxidants such as the hydroxyl radical ref robbins basic pathology 9th ed page 49 [/INST] question: Oxygen dependent killing is done through- | options: A: NADPH oxidase B: Superoxide dismutase C: Catalase D: Glutathione peroxidase | answer: A </s>