Glutamine glutamate dehydrogenase

The enzymes glutamate dehydrogenase, glutamine synthetase, and aminotransferases occupy central positions in amino acid biosynthesis. The combined effect of... 

S. E. Smith, B. L. St John, F. A. Smith, and D. j. D. Nicholas, Activity of glutamine synthetase and glutamate dehydrogenase in Trifolium subterraneum and Allium cepa L., effects of mycorrhizal infection and phosphorus nutrition. New Phytologist 99 211 (1985). 

Figure 8.17 The metabolism of branched-chain amino acids in muscle and the fate of the nitrogen and oxoacids. The a-NH2 group is transferred to form glutamate which is then aminated to form glutamine. The ammonia required for aminab on arises from glutamate via glutamate dehydrogenase, but originally from the transamination of the branded chain amino acids. Hence, they provide both nitrogen atoms for glutamine formation.

Figure 8.29 The initial reactions of glutamine metabolism in kidney, intestine and cells of the immune system. The initial reaction in all these tissues is the same, glutamine conversion to glutamate catalysed by glutaminase the next reactions are different depending on the function of the tissue or organ. In the kidney, glutamate dehydrogenase produces ammonia to buffer protons. In the intestine, the transamination produces alanine for release and then uptake and formation of glucose in the liver. In the immune cells, transamination produces aspartate which is essential for synthesis of pyrimidine nucleotides required for DNA synthesis otherwise it is released into the blood to be removed by the enterocytes in the small intestine or by cells in the liver.

A three-substrate, three-product enzyme-catalyzed reaction scheme in which the three substrates (A, B, and C) and three products (P, Q, and R) can bind to and be released in any order. A number of enzymes have been reported to have this mechanism for example, adenylosuccinate synthetase , glutamate dehydrogenase, glutamine synthetase , formyltetrahydrofolate synthetase, and tubulin tyrosine ligase . See Multisubstrate Mechanisms... 

See specific aminotransferase Glutamate as a substrate or product, GLUTAMATE DECARBOXYLASE GLUTAMATE DEHYDROGENASE GLUTAMATE SYNTHASE GLUTAMINE SYNTHETASE y-GLUTAMYL TRANSPEPTIDASE LEUCINE AMINOTRANSEERASE LYSINE 6-AMINOTRANSEERASE... 

Terms in bold are defined in aminotransferases 660 transaminases 660 transamination 660 pyridoxal phosphate (PLP) 660 oxidative deamination 661 l-glutamate dehydrogenase 661 glutamine synthetase 662 glutaminase 663 creatine kinase 664... 

Glucose 6-phosphate isomerase 279 Glucosidases—see lysozyme Glutamate dehydrogenase 167 Glutamine synthetase 298 Glyceraldehyde 3-phosphate... 

Examine the bioenergetics of the synthesis of glutamine synthesis from a-ketoglutarate via glutamate synthase or glutamate dehydrogenase (fig. 21.3). Is there a difference ... 

Concerning nitrate uptake and assimilation (Albuzio et al., 1986) in barley seedlings incubated with HS from a grassland soil and their fractions—nitrate reductase (NR), glutamate dehydrogenase (GDH),and glutamine synthetase (GS) activities— were analyzed together with the rate of nitrate uptake. The enzymatic activities turned out to be stimulated by the treatment of unfractioned humus extract with increases compared to controls of 65%, 35% and 45% respectively. 

Muscolo, A., Panuccio, M. R., Abenavoli, M. R., Concheri, G, and Nardi, S. (1996). Effect of molecular complexity and acidity of earthworm faeces humic fractions on glutamate dehydrogenase, glutamine synthetase and phosphoenolpyruvate carboxylase in Daucus carota II cells. Biol. Fertil. Soils 22, 83-88. 

Fig. 3. Assimilation of ammonia by (a) glutamate dehydrogenase and (b) glutamine synthetase.

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