Question

Which of the following is an example of competitive inhibition of an enzyme?

• A. Inhibition of succinic dehydrogenase by malonic acid.
• B. Inhibition of cytochrome oxidase by cyanide.
• C. Inhibition of hexokinase by glucose-6-phosphate.
• D. Inhibition of carbonic anhydrase by carbon dioxide.

Answer 1

The correct option is A Inhibition of succinic dehydrogenase by malonic acid.

Competitive inhibition is the type of inhibition, in which the inhibitor has structural similarity to the substrate molecule and competes with the substrate molecule for binding at the active site of the enzyme. Competitive inhibition is reversible. Malonate is a competitive inhibitor of the enzyme succinate dehydrogenase: malonate binds to the active site of the enzyme without reacting, and so competes with succinate, the usual substrate of the enzyme.
Cyanide is a non-competitive inhibitor and results in permanent inhibition of cytochrome oxidase.

So, the correct answer is 'Inhibition of succinic dehydrogenase by malonic acid.'