A 75-year-old woman complains of recent onset of chest pain, fever and productive cough with rust colored sputum. A chest X-ray reveals an infiltrate in the right middle lobe. Sputum cultures are positive for Streptococcus pneumoniae. Phagocytic cells in this patient's affected lung tissue generate bactericidal hypochlorous acid using which of the following enzymes?
High-Yield Explanation
Myeloperoxidase catalyzes the conversion of H2O2 , in the presence of a halide (e.g., chloride ion), to form hypochlorous acid. This powerful oxidant is a major bactericidal agent produced by phagocytic cells. Patients deficient in myeloperoxidase cannot produce hypochlorous acid and have an increased susceptibility to recurrent infections. -Catalase catalyzes H2O2. -Cyclooxygenase mediates the conversion of arachidonic acid to prostaglandins. -NADPH oxidase is involved in oxygen-free radical formation during the neutrophil respiratory burst. -Superoxide dismutase reduces the superoxide radical to H2O2