The Citric Acid Cycle Practice Test

The enzyme that catalyzes the conversion of citrate to isocitrate is aconitase. This reaction is the second step in the citric acid cycle and involves the rearrangement of citrate, a six-carbon compound, into isocitrate, which also has six carbons. Aconitase operates through a two-step mechanism: first, it converts citrate into cis-aconitate by removing a water molecule, and then it adds a water molecule back to produce isocitrate. This is an important step in the cycle, as it prepares the substrate for subsequent oxidative decarboxylation reactions, ultimately leading to the production of energy in the form of NADH and ATP.

Other enzymes listed facilitate different reactions within the citric acid cycle, but they do not carry out the specific conversion of citrate to isocitrate.