Citric Acid Cycle Practice Test 2026 - Free Biochemistry Practice Questions and Study Guide

The enzyme responsible for the conversion of isocitrate into alpha-ketoglutarate is isocitrate dehydrogenase. This enzyme catalyzes an oxidative decarboxylation reaction, where isocitrate, a six-carbon compound, is oxidized, and one carbon is released as carbon dioxide, resulting in the formation of the five-carbon molecule alpha-ketoglutarate. This reaction also involves the reduction of NAD+ to NADH, which is an important step in the energy production pathway of the citric acid cycle.

Isocitrate dehydrogenase plays a crucial role in regulating the flow of metabolites through the cycle and is one of the key points of control for the overall rate of the citric acid cycle. The identification of this enzyme highlights its importance in cellular respiration, linking the cycle's substrate transformations with energy production in cells through electron transport and the generation of ATP.