scholarly journals Some Properties of Glutamine Synthetase From the Nitrifying Bacterium Nitrosomonas Euro Paea

1981 ◽  
Vol 34 (6) ◽  
pp. 527 ◽  
Author(s):  
Basant Bhandari ◽  
DJD Nicholas
Keyword(s):  
Glutamine Synthetase ◽  
Glutamic Acid ◽  
Glutamate Dehydrogenase ◽  
Glutamate Synthase ◽  
Nitrosomonas Europaea ◽  
Main Route

Nitrosomonas europaea oxidizes ammonia to nitrite, thereby deriving energy for growth. Glutamate dehydrogenase (NADP+) (EC 1.4.1.4) is the main route for the incorporation of ammonia into glutamic acid, because glutamate synthase (NADPH) (EC 1.4.1.13) was not detected in cell-free extracts of N. europaea.

Ammonia, glutamine, and asparagine: a carbon–nitrogen interface

1988 ◽  
Vol 66 (10) ◽  
pp. 2103-2109 ◽  
Author(s):  
K. W. Joy
Keyword(s):  
Glutamine Synthetase ◽  
Glutamate Dehydrogenase ◽  
Higher Plants ◽  
Amino Nitrogen ◽  
Glutamate Synthase ◽  
Dinitrogen Fixation ◽  
Similar Function ◽  
Metabolic Processes ◽  
Organic Form ◽  
Primary Input

In plants, the primary input of nitrogen (obtained from the soil or from symbiotic dinitrogen fixation) occurs through the assimilation of ammonia into organic form. Synthesis of glutamine (via glutamine synthetase) is the major, and possibly exclusive, route for this process, and there is little evidence for the participation of glutamate dehydrogenase. A variety of reactions distribute glutamine nitrogen to other compounds, including transfer to amino nitrogen through glutamate synthase. In many plants asparagine is a major recipient of glutamine nitrogen and provides a mobile reservoir for transport to sites of growth; ureides perform a similar function in some legumes. Utilisation of transport forms of nitrogen, and a number of other metabolic processes, involves release of ammonia, which must be reassimilated. In illuminated leaves, there is an extensive flux of ammonia released by the photorespiratory cycle, requiring continuous efficient reassimilation. Aspects of ammonia recycling and related amide metabolism in higher plants are reviewed.

scholarly journals Distinctive properties and expression profiles of glutamine synthetase from a plant symbiotic fungus

2003 ◽  
Vol 373 (2) ◽  
pp. 357-368 ◽  
Author(s):  
Barbara MONTANINI ◽  
Marco BETTI ◽  
Antonio J. MÁRQUEZ ◽  
Raffaella BALESTRINI ◽  
Paola BONFANTE ◽  
...  
Keyword(s):  
Glutamine Synthetase ◽  
Glutamate Dehydrogenase ◽  
Expression Profiles ◽  
Glutamate Synthase ◽  
Synthetase Activity ◽  
Mrna Levels ◽  
Glutamine Synthetase Activity ◽  
Tuber Borchii ◽  
Root Cells ◽  
N Assimilation

Nitrogen retrieval and assimilation by symbiotic ectomycorrhizal fungi is thought to play a central role in the mutualistic interaction between these organisms and their plant hosts. Here we report on the molecular characterization of the key N-assimilation enzyme glutamine synthetase from the mycorrhizal ascomycete Tuber borchii (TbGS). TbGS displayed a strong positive co-operativity (n=1.7±0.29) and an unusually high S0.5 value (54±16 mM; S0.5 is the substrate concentration value at which v=½Vmax) for glutamate, and a correspondingly low sensitivity towards inhibition by the glutamate analogue herbicide phosphinothricin. The TbGS mRNA, which is encoded by a single-copy gene in the Tuber genome, was up-regulated in N-starved mycelia and returned to basal levels upon resupplementation of various forms of N, the most effective of which was nitrate. Both responses were accompanied by parallel variations of TbGS protein amount and glutamine synthetase activity, thus indicating that TbGS levels are primarily controlled at the pre-translational level. As revealed by a comparative analysis of the TbGS mRNA and of the mRNAs for the metabolically related enzymes glutamate dehydrogenase and glutamate synthase, TbGS is not only the sole messenger that positively responds to N starvation, but also the most abundant under N-limiting conditions. A similar, but even more discriminating expression pattern, with practically undetectable glutamate dehydrogenase mRNA levels, was observed in fruitbodies. The TbGS mRNA was also found to be expressed in symbiosis-engaged hyphae, with distinctively higher hybridization signals in hyphae that were penetrating among and within root cells.

scholarly journals Glutamine Synthetase-Glutamate Synthase Pathway and Glutamate Dehydrogenase Play Distinct Roles in the Sink-Source Nitrogen Cycle in Tobacco

2006 ◽  
Vol 140 (2) ◽  
pp. 444-456 ◽  
Author(s):  
Céline Masclaux-Daubresse ◽  
Michèle Reisdorf-Cren ◽  
Karine Pageau ◽  
Maud Lelandais ◽  
Olivier Grandjean ◽  
...  
Keyword(s):  
Glutamine Synthetase ◽  
Glutamate Dehydrogenase ◽  
Nitrogen Cycle ◽  
Glutamate Synthase

scholarly journals The roles of glutamate dehydrogenase, glutamine synthetase and three forms of glutamate synthase on nitrogen assimilation in various organs of Pisum arvense L.

2014 ◽  
Vol 60 (3-4) ◽  
pp. 295-302
Author(s):  
Genowefa Kubik-Dobosz
Keyword(s):  
Glutamine Synthetase ◽  
Glutamate Dehydrogenase ◽  
Nitrogen Assimilation ◽  
Decisive Role ◽  
Glutamate Synthase ◽  
Pisum Arvense ◽  
Age Dependent ◽  
The Individual

The activities of GDH, GS and three forms of GOGAT (NADH, NADPH or ferredoxin-dependent) were studied in the leaves, stems and roots of the <i>Pisum arvense</i>. GS and the individual forms of GOGAT dominated in the leaves of 7 day-old plants which were taking up NO<sub>3</sub><sup>-</sup> or NH<sub>4</sub><sup>+</sup> ions, while NADH-GDH dominated in the roots of these plants. In comparison with HNO<sub>3</sub><sup>-</sup> , NH<sub>4</sub><sup>+</sup> ions stimulated the activity of most of the enzymes of the GS/GOGAT and GDH pathways in stems and roots, while in and leaves this effect was age-dependent. The Fd-GOGAT located in leaves and stems was not regulated by NH<sub>4</sub><sup>+</sup> , which indicates that this enzyme is not likely to be directly involved in the assimilation of NH<sub>4</sub><sup>+</sup> ions that have been taken up. The obtained data indicate that at lower tissue NH<sub>4</sub><sup>+</sup> concentration a decisive role in nitrogen assimilation in leaves and stems is played by the GS/GOGAT pathway, while in the roots-by GDH and in less degree by GS, GOGAT. High amounts of accumulated NH<sub>4</sub><sup>+</sup> ions set off a detoxication mechanism which includes NADH-GDH, common to all tissues. Only in 7 day-old leaves did the detoxication of NH<sub>4</sub><sup>+</sup> take place with the involvement of NADH-GOGAT and NADPH-GOGAT.

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