scholarly journals Ethylene-Induced Increase in Glutamine Synthetase Activity and mRNA Levels in Hevea brasiliensis Latex Cells

1994 ◽  
Vol 105 (1) ◽  
pp. 127-132 ◽  
Author(s):  
V. Pujade-Renaud ◽  
A. Clement ◽  
C. Perrot-Rechenmann ◽  
J. C. Prevot ◽  
H. Chrestin ◽  
...  
Keyword(s):  
Glutamine Synthetase ◽  
Hevea Brasiliensis ◽  
Synthetase Activity ◽  
Mrna Levels ◽  
Glutamine Synthetase Activity

scholarly journals Dexamethasone regulates glutamine synthetase expression in rat skeletal muscles

1988 ◽  
Vol 255 (3) ◽  
pp. E397-E402 ◽  
Author(s):  
S. R. Max ◽  
J. Mill ◽  
K. Mearow ◽  
M. Konagaya ◽  
Y. Konagaya ◽  
...  
Keyword(s):  
Glutamine Synthetase ◽  
Skeletal Muscles ◽  
Northern Blot Analysis ◽  
Mrna Level ◽  
Synthetase Activity ◽  
Mrna Levels ◽  
Glutamine Synthetase Activity ◽  
Global Response ◽  
Tubulin Mrna ◽  
Major Increase

The regulation of glutamine synthetase expression by dexamethasone was studied in rat skeletal muscles. Daily administration of dexamethasone caused striking enhancement of glutamine synthetase activity in plantaris, soleus, and diaphragm muscles. Northern blot analysis revealed that the dexamethasone-mediated increase of glutamine synthetase activity was associated with dramatically increased levels of glutamine synthetase mRNA. Both glutamine synthetase activity and mRNA levels were significantly elevated in plantaris muscle at 0.5 mg.kg-1.day-1 of dexamethasone, a dose that approximates endogenous corticosteroid levels in animals under severe stress. Quantification of changes in glutamine synthetase mRNA on the basis of total mRNA (by oligo dT hybridization) also revealed a major increase in glutamine synthetase mRNA. Dexamethasone was without effect on beta-tubulin mRNA levels, indicating that glutamine synthetase induction is not part of a global response to glucocorticoids. Dexamethasone treatment resulted in only an approximately 15% increase in glutamine synthetase activity in heart; there was no change in glutamine synthetase mRNA level in this tissue. Thus glucocorticoids regulate glutamine synthetase gene expression in rat skeletal muscles.

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.

Respective effects of glucose and glutamine on the glutamine synthetase activity of human skin fibroblasts

1991 ◽  
Vol 102 (2) ◽  
Author(s):  
Th�ophile Soni ◽  
Claire Wolfrom ◽  
Samia Guerroui ◽  
Nicole Raynaud ◽  
Jos�phine Poggi ◽  
...  
Keyword(s):  
Glutamine Synthetase ◽  
Human Skin ◽  
Skin Fibroblasts ◽  
Synthetase Activity ◽  
Glutamine Synthetase Activity ◽  
Human Skin Fibroblasts

Control of nitrogen assimilation in Stichococcus bacillaris by growth conditions

1987 ◽  
Vol 65 (3) ◽  
pp. 432-437 ◽  
Author(s):  
Iftikhar Ahmad ◽  
Johan A. Hellebust
Keyword(s):  
Glutamine Synthetase ◽  
Nitrogen Assimilation ◽  
Continuous Light ◽  
Synthetase Activity ◽  
Glutamine Synthetase Activity ◽  
Dark Cycle ◽  
Continuous Darkness ◽  
Cell Carbon ◽  
Stichococcus Bacillaris ◽  
Mixotrophic Conditions

Stichococcus bacillaris Naeg. (Chlorophyceae) grown on a 12 h light: 12 h dark cycle divides synchronously under photoautotrophic conditions and essentially nonsynchronously under mixotrophic conditions. Photoassimilation of carbon under photoautotrophic conditions was followed by a decline in cell carbon content during the dark period, whereas under mixotrophic conditions cell carbon increased throughout the light–dark cycle. The rates of nitrogen assimilation by cultures grown on either nitrate or ammonium declined sharply during the dark, and these declines were most pronounced under photoautotrophic conditions. Photoautotrophic cells synthesized glutamine synthetase and NADPH – glutamate dehydrogenase (GDH) exclusively in the light, whereas in mixotrophic cells about 20% of the total synthesis of these enzymes during one light–dark cycle occurred in the dark. NADH–GDH was synthesized almost continuously over the entire light–dark cycle. In the dark, both under photoautotrophic and mixotrophic conditions, the alga contained more than 50% of glutamine synthetase in an inactive form, which was reactivated in vitro in the presence of mercaptoethanol and in vivo after returning the cultures to the light. The thermal stability of glutamine synthetase activity was less in light-harvested cells than in dark-harvested cells. The inactivation of glutamine synthetase did not occur in cultures growing either heterotrophically in continuous darkness or photoautotrophically in continuous light. This enzyme appears to be under thiol control only in cells grown under alternating light–dark conditions, irrespective of whether this light regime results in synchronous cell division or not.

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