Which enzyme is alpha-ketoglutarate dehydrogenase very similar to?

Alpha-ketoglutarate dehydrogenase is very similar to pyruvate dehydrogenase because both enzymes belong to a class of multi-subunit enzyme complexes that catalyze the oxidative decarboxylation of their respective substrates.

In the case of alpha-ketoglutarate dehydrogenase, it catalyzes the conversion of alpha-ketoglutarate to succinyl-CoA in the citric acid cycle, while pyruvate dehydrogenase converts pyruvate to acetyl-CoA. Both reactions involve the decarboxylation of a 5-carbon intermediate, producing carbon dioxide as a byproduct and forming a high-energy thioester bond with Coenzyme A.

Additionally, both of these enzymes utilize similar cofactors, including thiamine (vitamin B1), lipoic acid, and coenzyme A, and involve similar regulatory mechanisms. This resemblance in both their structure and function highlights their evolutionary relationship and role in energy metabolism.