Question

What citric acid cycle intermediates would accumulate in the presence of malonate?

Short answer

In presence of malonate, the intermediates accumulated would be succinyl-CoA, citrate, α – ketoglutarate, oxaloacetate, malate, and isocitrate.

Step-by-step solution

Succinate dehydrogenase

Succinate dehydrogenase (SDH) or succinate-coenzyme Q reductase (SQR) or respiratory complex II is an enzyme complex found in the inner mitochondrial membrane of eukaryotic and many bacterial cells.

It is the only enzyme that works in the citric acid cycle and the electron transport chain at the same time.In the citric acid cycle, it catalyzes the formation of fumarate from succinate.

Effect on citric acid cycle in the presence of malonate

Malonate inhibits succinate dehydrogenase in a competitive manner. As a result, all the intermediates generated just before succinyl-CoA succinate conversion would build up. Thus, the intermediates such as succinyl-CoA, citrate, -ketoglutarate, oxaloacetate, malate, and isocitrate will be accumulated in presence of malonate.