Which one of the following would you predict is an allosteric inhibitor of the Krebs cycle enzyme, α-ketoglutarate dehydrogenase? A) citric acidB) α-ketoglutaric acidC) NAD+D) NADHE) ADP

D) NADH

Explanation:

Allosteric inhibitor alters protein conformation in the active site of the enzyme by binding to allosteric site. It consequently changes shape of the active site due to which the enzyme is unable to perform catalytic activity and become inactive.

The reaction catalyzed by α-Ketoglutarate dehydrogenase is:

α-Ketoglutarate + NAD⁺ + CoA-SH ⇒ succinyl-CoA + NADH + H⁺ + CO₂

α-Ketoglutarate dehydrogenase is inhibited by both succinyl CoA and NADH which are the products of reaction which it catalyzes. In addition to it, α-ketoglutarate dehydrogenase is also inhibited by high energy charge.