Question

Which of the following helps in generating the oxygen (respiratory) burst in neutrophils?

• A. Superoxide dismutase
• B. NADPH oxidase
• C. Peroxidase
• D. Glutathione reductase

Hint:

Think of the enzyme that makes superoxide and whose defect causes chronic granulomatous disease.

Answer 1

The Correct Option is B

Step 1: Define the respiratory burst. After a neutrophil engulfs a microbe, it rapidly consumes oxygen to make reactive oxygen species for killing, an event called the oxidative or respiratory burst.
Step 2: Identify the initiating enzyme. The burst is started by the membrane-bound enzyme NADPH oxidase, which transfers electrons from NADPH to molecular oxygen, producing superoxide anion (O2-).
Step 3: Trace the downstream products. Superoxide is then converted to hydrogen peroxide, and myeloperoxidase uses peroxide and chloride to form hypochlorous acid, the potent microbicidal agent.
Step 4: Exclude the other enzymes. Superoxide dismutase and glutathione reductase are antioxidant/detoxifying enzymes, and peroxidase acts downstream on already-formed peroxide, none of them initiate the burst.
Step 5: Note the clinical link. A defect in NADPH oxidase causes chronic granulomatous disease, confirming its central role.
Conclusion: NADPH oxidase generates the oxygen burst, so the correct answer is option 2.