What is the role of succinyl CoA synthetase in the citric acid cycle?

The role of succinyl CoA synthetase in the citric acid cycle is to catalyze the conversion of succinyl CoA to succinate. This reaction is significant because it is one of the few steps in the citric acid cycle that directly generates energy. During this conversion, a molecule of GDP (or ADP) is phosphorylated to form GTP (or ATP), which can easily be converted to ATP, thus reflecting the cycle's contribution to the cell's energy currency.

Succinyl CoA is a high-energy thioester compound, and the conversion to succinate involves the release of energy that is harnessed to drive the phosphorylation of GDP. The resulting succinate then continues on through the cycle, eventually being reoxidized to regenerate oxaloacetate. This step is crucial for maintaining the continuity of the cycle and ensuring that energy production continues efficiently.