scholarly journals The role of glutamine synthetase, glutamate synthase and glutamate dehydrogenase in ammonia assimilation by the mycorrhizal fungus Pisolithus tinctorius

1989 ◽  
Vol 46 (Supplement) ◽  
pp. 706s-710s ◽  
Author(s):  
J. L. Kershaw ◽  
G. R. Stewart
Keyword(s):  
Glutamine Synthetase ◽  
Glutamate Dehydrogenase ◽  
Mycorrhizal Fungus ◽  
Glutamate Synthase ◽  
Pisolithus Tinctorius ◽  
Ammonia Assimilation

Enzymes of ammonia assimilation in Rhizobium leguminosarum bacteroids

1975 ◽  
Vol 21 (7) ◽  
pp. 1009-1012 ◽  
Author(s):  
W. G. W. Kurz ◽  
D. A. Rokosh ◽  
T. A. Larue
Keyword(s):  
Glutamine Synthetase ◽  
Glutamate Dehydrogenase ◽  
Rhizobium Leguminosarum ◽  
Glutamate Synthase ◽  
Dinitrogen Fixation ◽  
Ammonia Assimilation ◽  
Enzymes Of Ammonia Assimilation

The activities of the following enzymes were studied in connection with dinitrogen fixation in pea bacteroids: glutamine synthetase (L-glutamate:ammonia ligase (ADP-forming)) (EC 6.3.1.2) (GS); glutamate dehydrogenase (NADP+) (L-glutamate:NADP+ oxidoreductase (deaminating)) (EC 1.4.1.4) (GDH); glutamate synthase (L-glutamine:2-oxoglutarate aminotransferase (NADPH-oxidizing)) (EC 2.6.1.53) (GOGAT). GS activity was high throughout the growth of the plant and GOGAT activity was always low. It is unlikely that GDH or the GS–GOGAT pathway can account for the incorporation of ammonia from dinitrogen fixation in the pea bacteroid.

Enzymes of Nitrogen Metabolism in Legume Nodules: a Comparative Study

1978 ◽  
Vol 5 (5) ◽  
pp. 553 ◽  
Author(s):  
MJ Boland ◽  
HM Fordyce ◽  
RM Greenwood
Keyword(s):  
Glutamine Synthetase ◽  
Comparative Study ◽  
Glutamate Dehydrogenase ◽  
Nitrogen Metabolism ◽  
Glutamate Synthase ◽  
Ammonia Assimilation ◽  
Legume Species

Levels of activity of glutamine synthetase, glutamate dehydrogenase and NADH-dependent glutamate synthase in nodule cytoplasm extracts of twelve herbaceous legume species have been measured. Nodules of all species contained substantial quantities of glutamine synthetase. Levels of glutamate synthase were found to be between 7 and 100% of those of glutamine synthetase, while levels of glutamate dehydrogenase varied widely between 0.2 and 150% of those of glutamine synthetase. The estimated Km for hydroxylamine of glutamine synthetase was found to vary between 0.02 and 0.5 mM in nine species tested, while that of glutamate dehydrogenase for ammonia varied between 0.03 M and 0.1 M in the four species containing significant levels of that enzyme. It is proposed that the pathway of ammonia assimilation via glutamine synthetase and NADH-dependent glutamate synthase-catalysed reactions is universal in legume nodule metabolism.

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 Role of the complex upstream region of the GDH2 gene in nitrogen regulation of the NAD-linked glutamate dehydrogenase in Saccharomyces cerevisiae.

1991 ◽  
Vol 11 (12) ◽  
pp. 6229-6247 ◽  
Author(s):  
S M Miller ◽  
B Magasanik
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Glutamine Synthetase ◽  
Nitrogen Source ◽  
Glutamate Dehydrogenase ◽  
Regulatory System ◽  
Sole Source ◽  
Lacz Fusion ◽  
Upstream Region ◽  
In Cells

We analyzed the upstream region of the GDH2 gene, which encodes the NAD-linked glutamate dehydrogenase in Saccharomyces cerevisiae, for elements important for the regulation of the gene by the nitrogen source. The levels of this enzyme are high in cells grown with glutamate as the sole source of nitrogen and low in cells grown with glutamine or ammonium. We found that this regulation occurs at the level of transcription and that a total of six sites are required to cause a CYC1-lacZ fusion to the GDH2 gene to be regulated in the same manner as the NAD-linked glutamate dehydrogenase. Two sites behaved as upstream activation sites (UASs). The remaining four sites were found to block the effects of the two UASs in such a way that the GDH2-CYC1-lacZ fusion was not expressed unless the cells containing it were grown under conditions favorable for the activity of both UASs. This complex regulatory system appears to account for the fact that GDH2 expression is exquisitely sensitive to glutamine, whereas the expression of GLN1, coding for glutamine synthetase, is not nearly as sensitive.

The green hydra symbiosis and ammonium. I. The role of the host in ammonium assimilation and its possible regulatory significance

1986 ◽  
Vol 229 (1256) ◽  
pp. 299-314 ◽  
Keyword(s):  
Glutamine Synthetase ◽  
Glutamate Dehydrogenase ◽  
Ammonium Assimilation ◽  
Nitrogen Status ◽  
Continuous Darkness ◽  
Methionine Sulphoximine ◽  
Vacuolar Ph ◽  
Regulatory Significance

Evidence for ammonium assimilation by host and symbiont in algal─invertebrate symbioses is summarized and critically evaluated. The host from all strains of hydra studied possessed glutamine synthetase (GS) and glutamate dehydrogenase (GDH) activities. The host from associations with high maltose releasing algae (E/E, E /3N8) had high GS and low GDH activities, whereas aposymbiotic animals (EALB) and the association with a low maltose releasing alga (E/NC) had low GS and high GDH activities. The observation that symbiotic animals do not release ammonium in the light, whereas aposymbiotic animals release substantial amounts, may be explicable on the basis of variation in the ability of the host to assimilate ammonium. Thus, the photosynthetic inhibitor DCMU had no effect on ammonium release by symbiotic animals, with the possible exception of E/NC. Methionine sulphoximine (MSO) completely inhibited GS activity from EALB both in vitro and in vivo . In the presence of MSO, ammonium release was enhanced in both EALB and E/E. In continuous darkness, an increase in ammonium released by symbiotic animals (E/E) was correlated with a decrease in host GS activity. It is suggested that the evidence is consistent with host and not symbiont assimilation of ammonium. A model of symbiont regulation is proposed based on regulation of ammonium supply as a means of controlling both perialgal vacuolar pH and symbiont nitrogen status.

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