Glutamate synthase glutamine synthetase

Baron, A. C., Tobin, T. H., WaHsgrove, R. M., and Tobin, A. K. (1994). AmetaboHc control analysis of the glutamine synthetase/glutamate synthase cycle in isolated barley Elordeum vulgare L.) chloroplasts. Plant Physiol. 105, 415-424. 

The short-lived radionuclide, has been extremely useful in studies of N2 fixation and NH4 assimilation. Wolk and his collaborators have demonstrated that the glutamine synthetase/glutamate synthase pathway is the major assimilatory route for NH4 in N2-fixing cultures of Anabaena and many other cyanobacteria. They have extended these studies to show that the labeling pattern observed after exposure of detached or attached soybean root nodules to [ N]N2 was similar to that observed in Anabaena. On this basis Meeks et al. (19) concluded that the primary pathway for assimilating NH4" derived from N2 in soybean nodules involves the sequential assimilatory activities of glutamine synthetase and glutamate synthase. 

Figure 11 Nitrogen sources and metabolic pathways in marine phytoplankton. Solid circles are transporters. Boxes are the catalytic enzymes and open circles are metals associated with each enzyme. Ur, Urease NR, Nitrate Reductase NiR, Nitrite Reductase AAOx, amino acid oxidase AmOx, amine oxidase GS-GOGAT, Glutamine Synthetase- Glutamate oxy-glutarate aminotransferase (or glutamate synthase).

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... 

The net reaction of glutamine synthetase and glutamate synthase (Eqns 22-1 and 22-2) is... 

Terms in bold are defined in the nitrogen cycle 834 nitrogen fixation 834 symbionts 834 nitrogenase complex 835 leghemoglobin 836 glutamine synthetase 838 glutamate synthase 838 glutamine amidotransferases 840 5-phosphoribosyl-l-... 

Fig. 1. The nitrate assimilation pathway in higher plants. The pathway of nitrate assimilation in the tobacco leaf is illustrated. In some other species an additional cytosolic GS is found in the leaf. The pathway in plant roots is more poorly documented and more variable GS in roots is mostly cytosolic, and some enzymes such as GOGAT are found as isoforms utilising alternate reducing substrates. T, expected nitrate carrier NR, nitrate reductase NiR, nitrite reductase GS, glutamine synthetase GOGAT, glutamate synthase Fd, ferredoxin Gin, glutamine Glu, glutamate.

Chen, F.-L., Bennett, M.J. Cullimore, J.V. (1990). Effect of the nitrogen supply on the activities of isoenzymes of NADH-dependent glutamate synthase and glutamine synthetase in root nodules of Phaseolus vulgaris L. Journal of Experimental Botany 41, 1215-21. 

Berger, M.G., Sprengart, M.L., Kusnan, M. and Fock, H.P. (1986) Ammonia fixation via glutamine synthetase and glutamate synthase in the crassulacean acid metabolism plant, Cissus quadrangularis. Plant Physiol., 81, 356-60. 

Wang, R. and Nicholas, D.J.D. (1985) Some properties of glutamine synthetase and glutamate synthase from Derxia gummosa. Phytochemistry, 24,1133-40. 

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