Succinate dehydrogenase catalyzes the conversion of succinate to fumarate in the TCA cycle. Malonate, a structural analogue of succinate, strongly inhibits this enzyme. When the concentration of succinate is progressively increased in the presence of a fixed amount of malonate, the inhibition is overcome and maximum velocity is eventually restored. This pattern describes which of the following enzyme inhibition kinetics?
- A Non-competitive inhibition with decreased Vmax and unchanged Km
- B Competitive inhibition with increased apparent Km and unchanged Vmax ✓
- C Uncompetitive inhibition with decreased Km and decreased Vmax
- D Substrate inhibition with sigmoidal velocity curve
Correct answer: B. Competitive inhibition with increased apparent Km and unchanged Vmax
Explanation
Malonate is a classic competitive inhibitor of succinate dehydrogenase because it structurally resembles succinate and competes for the same active site. In competitive inhibition, excess substrate can displace the inhibitor, restoring Vmax; only the apparent Km is increased. The Lineweaver-Burk plot shows lines crossing on the y-axis, confirming unchanged Vmax.
Reference: Harper's Illustrated Biochemistry, 32nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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