This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Oxygen dependent bacterial killing, Subject name: Pathology
[{'content': "All of the following molecules/enzymes may contribute in generating free oxygen radicals within neutrophils for killing intracellular bacteria, except- \nSelect and explain. \nA. Nitric oxide, B. Fenton's reaction, C. NADPH oxidase, D. Catalase", 'role': 'user'}, {'content': 'Answer: D \nExplanation: * Catalase, present in peroxisomes, catalyzes the decomposition of hydrogen peroxide (2H2O2 - O2 + 2H2O). It is one of the most active enzymes known, capable of degrading millions of molecules of H2O2 per second. *iNOS, the type that is involved in microbial killing, is expressed when macrophages are activated by cytokines (e.g., IFN-g)or microbial products, and induces the production of NO.', 'role': 'assistant'}]