α-Ketoglutarate dehydrogenase (α-KGDH) is a multienzyme complex localized to the mitochondria. This integrated enzyme is made up of many units of thiamine pyrophosphate-dependent dehydrogenase (E1), dihydrolipoamide dehydrogenase (E3), and dihydrolipoamide succinyl transferase (E2).
α-Ketoglutarate dehydrogenase (α-KGDH) is a key enzyme of bioenergetic processes and a controlling unit of metabolic flux through the Krebs cycle or tricarboxylic acid (TCA) cycle. It catalyzes the oxidative decarboxylation of α-ketoglutarate (KG) to succinyl-CoA by releasing reduced nicotinamide adenine dinucleotide (NADH). It is the rate-limiting reaction of the TCA cycle. This reaction contributes to the electrons of the respiratory chain and requires thiamine pyrophosphate as a cofactor. The reduction of NAD (nicotinamide adenine dinucleotide) is observed to determine its reaction rate. α-KGDH from porcine has an optimum pH range of 6.6–7.4. This enzyme is inhibited by oxidative stress and results in a metabolic deficiency. However, α-KGDH is also known to produce reactive oxygen species (ROS) leading to oxidative stress. Defective or limited levels of α-KGDH cause several neurodegenerative diseases such as Alzheimer′s disease.
