Glutamic 2-oxoglutarate dehydrogenase

Figure 6.3. GABA shunt as an alternative to a-ketoglutarate dehydrogenase in the citric acid cycle. 2-Oxoglutarate dehydrogenase, EC 1.2.4.2 glutamate decarboxylase, EC 4.1.1.15 GABA aminotransferase, EC 2.6.1.19 and succinic semialdehyde dehydrogenase, ECl.2.1.16.

Kawahara Y, Takahashi-Fuke K, Shimizu E, Nakamatsu T, Nakamori S. (1997). Relationship between the glutamate production and the activity of 2-oxoglutarate dehydrogenase in Brevibacterium lactofermentum. Biosci Biotechnol Biochem, 61, 1109-1112. 

Schultz C, Niebisch A, Gebel L, Bott M. (2007). Glutamate production by Corynebacterium glutamicum dependence on the oxoglutarate dehydrogenase inhibitor protein OdhI and protein kinase PknG. Appl Microbiol Biotechnol, 76, 691-700. 

Keywords Anaplerotic pathways Corynebacterium glutamicum Glutamate Metabolic engineering NCgll221 OdhI 2-Oxoglutarate dehydrogenase complex... 

Figure 11.4 Metabolic reactions related to glutamic acid biosynthesis in C. glutamicum. GS, glutamine synthetase GOGAT, glutamate synthase (glutamate-oxoglutarate aminotransferase) and GDH, glutamate dehydrogenase.

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

Figure 11.5 Metabolic pathways related to glutamic acid production in C glutamicum. ICDH, isocitrate dehydrogenase, ODHC, 2-oxoglutarate dehydrogenase complex GDH, glutamate dehydrogenase PPC, phosphoenolpyruvate carboxylase and PC, pyruvate carboxylase.

It could, therefore, be that all the nitrogen of respired protein can, in this way, be canalised into the formation of glutamic acid and then be released as ammonia by the glutamic acid dehydrogenase enzyme. We are not certain that this is the case o-oxoglutaric acid, and oxalacetic acid (corresponding to the amino acid aspartic acid) and pyruvic acid (corresponding to alanine) are acids of the Krebs... 

Other bacteria such as E. coli assimilate ammonia by incorporating it directly into a-oxoglutarate in a reaction catalysed by glutamate dehydrogenase (GDH). This reaction can be written as... 

The glutamate which results form the reaction remains in the mitochondria where it is oxidatively deaminated by glutamate dehydrogenase to form 2-oxoglutarate. 

Figure 8.25 Excess ammonia in the muscle is used to form alanine. Ammonia is released from several reactions and is incorporated into alanine via glutamate dehydrogenase and transamination. OG - oxoglutarate. Alanine is released into the blood from volece it is removed by the liver.

It is a substrate for the formation of glutamate from oxoglutarate in a reaction catalysed by the enzyme glutamate dehydrogenase. 

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