Which of the following steps of the Citric Acid Cycle involves decarboxylation?

The oxidative decarboxylation of isocitrate is a key step in the Citric Acid Cycle where carbon dioxide (CO2) is released. During this process, isocitrate is oxidized to form alpha-ketoglutarate, and this reaction is catalyzed by the enzyme isocitrate dehydrogenase.

In this reaction, the oxidation results in the loss of a carboxyl group in the form of CO2, classifying it specifically as a decarboxylation reaction. This step not only contributes to the cycle's overall function of energy production through the subsequent reactions, but it is also pivotal for the regulation of the cycle itself, often responding to the availability of NAD+ and the energy needs of the cell.

The significance of this step extends beyond mere carbon loss; it also plays a crucial role in linking the decarboxylation phase of cellular respiration to the reduction of NAD+, thereby facilitating the production of NADH, which will later contribute to ATP synthesis during oxidative phosphorylation.