In a metabolic pathway, succinate dehydrogenase catalyzes the conversion of succinate to fumarate. The reaction is inhibited by malonic acid, a substance that resembles succinate but cannot be acted upon by succinate dehydrogenase. Increasing the amount of succinate molecules to those of malonic acid reduces the inhibitory effect of malonic acid. What role does malonic acid play with respect to succinate dehydrogenase?
A) Malonic acid is a competitive inhibitor.
B) Malonic acid blocks the binding of fumarate.
C) Malonic acid is a noncompetitive inhibitor.
D) Malonic acid is an allosteric regulator.

Question

Quizplus · Accepted Answer

Malonic acid is structurally similar to succinate and can compete with succinate for binding to the enzyme. This is characteristic of a competitive inhibitor. This leads to a decrease in the activity of the enzyme and slows down the metabolic pathway. Increasing the amount of succinate molecules allows for more competition with malonic acid and reduces its inhibitory effect.

In a Metabolic Pathway, Succinate Dehydrogenase Catalyzes the Conversion of Succinate