Question

Inhibition of succinate dehydrogenase is caused by
malonate. What will happen to the Km of the
enzyme when excess of succinate is added?
(1). Km will increase and Vmax constant
(2) Km will decrease and Vmax constant
(3) Km constant and Vmax decreases
(4) Km constant and Vmax increases
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Answer 1

Answer:1

Explanation: It is a case of competitive inhibition... Here rate is decreased and vmax is constant... Which means Km value has to be increased...as It is affected by substrate concentration

Answer 2

Answer:

The correct answer is (2) Km will decrease and Vmax will be constant.

Explanation:

This is an example of competitive inhibition of succinate dehydrogenase by its competitive inhibitor, malonate. Malonate binds to the active site of the enzyme thereby occupying the space of the substrate.

Therefore, less active enzyme is available for binding to the substrate and the Km increases, however, the Vmax remains constant.

When an excess of the substrate( succinate) is added, inhibition reduces and more substrate binds to the enzyme( due to a higher concentration). This reduces the Km( affinity increases), but Vmax remains constant.