2-Oxoglutarate dehydrogenase complex enzyme activity

In aerobic environments, eukaryotes and many eubacteria oxidatively decarboxylate the 2-oxoacids via pyruvate and 2-oxoglutarate dehydrogenase complexes [36]. For comparison with the archaebacterial oxidoreductases, the catalytic mechanism of these complexes is also shown in Fig. 4. Three enzymic activities are involved, catalysed by three distinct enzymes a 2-oxoacid decarboxylase (El), a dihydrolipoyl acyltransferase (E2) and dihydrolipoamide dehydrogenase (E3). Multiple copies of these three enzymes are found in each complex molecule, resulting in relative molecular masses in excess of 2x10 ... 

Relationship between Enzyme Activity of the 2-Oxoglutarate Dehydrogenase Complex and Glutamic Acid Production... 

Now this reaction is effectively a repeat of the pyruvate acetyl-CoA oxidative decarboxylation we saw at the beginning of the Krebs cycle. It similarly requires thiamine diphosphate, lipoic acid, coenzyme A and NAD+. A further feature in common with that reaction is that 2-oxoglutarate dehydrogenase is also an enzyme complex comprised of three separate enzyme activities. 2-Oxoglutarate is thus transformed into succinyl-CoA, with the loss of... 

ThDP plays a crucial role as coenzyme for several enzymes and enzyme complexes such as transketolase (EC 2.2.1.1) and the enzyme complexes pyruvate (EC 1.2.4.1) and 2-oxoglutarate (EC 1.2.4.2) dehydrogenases, present in nearly all organisms. They play important catabolic roles and are key actors in cell energy metabolism (Figure 5.1). Reduced activity of these enzymes as a consequence of thiamin deficiency results in decreased glucose oxidation. As the brain heavily relies on oxidative metabolism, it is more severely affected by thiamin deficiency than other organs. 

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