Which classic example illustrates competitive inhibition of an enzyme by a substrate analog?
Answer and explanation
Correct answer: B. Inhibition of succinic dehydrogenase by malonate
- Step 1: Succinic dehydrogenase catalyzes the dehydrogenation of succinate to fumarate in the Krebs cycle.
- Step 2: Malonate has a three-carbon dicarboxylic structure () that closely mimics succinate ().
- Step 3: Malonate binds to the active site of succinate dehydrogenase without undergoing oxidation, acting as a textbook competitive inhibitor.
Answer
Inhibition of succinic dehydrogenase by malonate.
Why not the others: Inhibition of hexokinase by glucose-6-phosphate is feedback allosteric inhibition; Cyanide inhibiting cytochrome oxidase is irreversible non-competitive toxicity; Acetazolamide inhibiting carbonic anhydrase is a therapeutic non-competitive/mixed blocker.
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