Influence of nitrogen source and growth status on glutamine synthetase and glutamate synthase activity in Mycobacterium avium

1985 ◽  
Vol 31 (3) ◽  
pp. 211-213
Author(s):  
Charlotte M. McCarthy ◽  
Maria E. Alvarez
Keyword(s):  
Glutamine Synthetase ◽  
Ammonium Chloride ◽  
Mycobacterium Avium ◽  
Cultured Cells ◽  
Specific Activity ◽  
Glutamate Synthase ◽  
Ammonia Concentration ◽  
Apparent Difference ◽  
Growth Status ◽  
Chloride Concentrations

An investigation was made of the activity of glutamine synthetase and glutamate synthase from batch-cultured cells of Mycobacterium avium. The bacteria were grown in medium with ammonium chloride concentrations of 0, 0.1, 0.25, 1, 5, or 25 μmol/mL or with glutamine at 0.1 or 1 μmol/mL. The specific activity of the two enzymes was determined at 0, 22, 45, and 70 h of incubation. Regardless of the ammonia concentration in the medium, glutamate synthase specific activity was two to five times higher in extracts from elongating cells, incubated 22 h, than in those from shortened cells, incubated 45 or 70 h. In contrast, there was no apparent difference in glutamine synthetase specific activity with regard to culture age; however, glutamine synthetase specific activity varied inversely with the concentration of ammonium chloride in the medium. Cells grown in glutamine had high activity of glutamine synthetase.

Corrigendum to: Ammonium metabolism in Selaginella bryopteris in response to dehydration-rehydration and characterisation of desiccation tolerant, thermostable, cytosolic glutamine synthetase from plant

2021 ◽  
Vol 48 (3) ◽  
pp. 358
Author(s):  
Kamal K. Singh ◽  
Shyamaprasad Saha ◽  
Ram C. Kadiravana ◽  
Deepika Mazumdar ◽  
Vijeta Rai ◽  
...  
Keyword(s):  
Glutamine Synthetase ◽  
Metabolic Regulation ◽  
Specific Activity ◽  
Higher Plants ◽  
Glutamate Synthase ◽  
Immunoblot Analysis ◽  
Primary Metabolism ◽  
Ammonium Metabolism ◽  
Free Ammonium ◽  
Selaginella Bryopteris

Water deficit (WD) has adverse effects on plant growth, and acclimation requires responses allowing primary metabolism to continue. Resurrection plants can serve as model system to gain insight into metabolic regulation during WD. We herein report the response of a resurrection lycophyte, Selaginella bryopteris, to dehydration-rehydration cycle with emphasis on ammonium metabolism. Dehydration of S. bryopteris fronds resulted in decrease of total protein and increase of free ammonium levels and the effect was reversed on rehydration. The proline content increased twice after 24 h of dehydration, which again recovered to background levels comparable to that at full turgor state. The specific activity of glutamine synthetase (GS) didn’t change significantly till 6 h and then declined by 21% after 24 h of dehydration, whereas specific activities of glutamate synthase (GOGAT) and aminating glutamate dehydrogenase (GDH) were enhanced significantly during dehydration. The deaminating activity of GDH also increased during dehydration albeit at a slower rate. Immunoblot analysis indicated overexpression of GS and GDH polypeptides during dehydration and their levels declined on rehydration. The results suggested significant role of GDH along with GS/GOGAT in production of nitrogen-rich amino acids for desiccation tolerance. Unlike higher plants S. bryopteris expressed GS only in cytosol. The enzyme had pH and temperature optima of 5.5 and 60°C, respectively, and it retained 96% activity on preincubation at 60°C for 30 min indicating thermostability. Hence, like higher plants the cytosolic GS from S. bryopteris has a conserved role in stress tolerance.

Osmoregulation in Rhizobium meliloti: characterization of enzymes involved in glutamate synthesis

1990 ◽  
Vol 36 (7) ◽  
pp. 469-474 ◽  
Author(s):  
Rigoberto Gonzalez-Gonzalez ◽  
James L. Botsford ◽  
Thomas Lewis
Keyword(s):  
Glutamine Synthetase ◽  
Osmotic Stress ◽  
Specific Activity ◽  
Rhizobium Meliloti ◽  
Glutamate Synthase ◽  
The Other ◽  
Glutamine Synthetase Activity ◽  
Biochemical Basis ◽  
Glutamic Dehydrogenase ◽  
Glutamate Synthesis

Rhizobium meliloti, like many bacteria, accumulates elevated levels of glutamate when osmotically stressed. The biochemical basis for this increase in glutamate production was investigated. Enzymes involved in glutamate synthesis, including glutamine synthetase, glutamate synthase, and glutamic dehydrogenase, were characterized in dialyzed crude cell-free extracts. A transaminase activity, which uses branched chain amino acids for the amination of 2-ketoglutaric acid, was also characterized. With the exception of glutamic dehydrogenase, the specific activity of the enzymes did not vary more than 4-fold in response to the available source of nitrogen or supplemental glutamate. Glutamic dehydrogenase activity was 13-fold greater when cells grew with 10 mM [Formula: see text] than when cells grew with 0.5 mM [Formula: see text]. Glutamate synthase was repressed 2-fold when cells grew with supplemental glutamate. Conversely, this enzyme was derepressed 2× when cells grew with 0.5 mM [Formula: see text] or nitrate. Growing cells in minimal defined medium with 400 mM NaCl to cause osmotic stress had little effect on the specific activity of any of the enzymes. The addition of K+ to the reactions stimulated heat-stable glutamine synthetase activity, but inhibited the other enzymes. Glutamate synthase was inhibited to a limited extent by several intermediates in the Krebs' cycle and very severely by glyoxylate. The addition of 10 mM glutamate to the reaction inhibited glutamate synthase 20%, but had no effect on the other enzymes. Key words: enzymes, glutamate synthesis, osmotic stress.

Glutamine synthetase from Mycobacterium avium

1984 ◽  
Vol 30 (3) ◽  
pp. 353-359 ◽  
Author(s):  
Maria E. Alvarez ◽  
C. M. McCarthy
Keyword(s):  
Enzyme Activity ◽  
Glutamine Synthetase ◽  
Nitrogen Source ◽  
Mycobacterium Avium ◽  
Specific Activity ◽  
Sedimentation Coefficient ◽  
Ammonia Assimilation ◽  
Methionine Sulfoximine ◽  
Synthetase Activity ◽  
Glutamine Synthetase Activity

Mycobacterium avium was previously shown to be dependent upon ammonia or glutamine as a nitrogen source. In an effort to assess the physiology of ammonia assimilation by M. avium, a characterization of its glutamine synthetase was performed. The enzyme from M. avium was purified by streptomycin sulfate treatment, ammonium sulfate precipitation, and affinity chromatography. The enzyme was unusual in that it had a pH optimum of 6.4 and maximum enzyme activity was obtained between 50 and 60 °C as shown by the transferase assay. The glutamine synthetase activity from batch-cultured cells decreased with increasing concentration of ammonium chloride in the range of 0.25–5 μ mol/mL of medium, which demonstrated a response to environmental supply of a nitrogen source. The mycobacterial enzyme was similar to the other bacterial glutamine synthetases in terms of molecular weight and sedimentation coefficient which were 600 000 and 19.5 S, respectively, and enzyme activity was lost by treatment with a glutamate analog, methionine sulfoximine. The isoelectric point was, however, pH 4.5. Treatment of the enzyme with snake venom phosphodiesterase resulted in an increase in specific activity. AMP was released by the phosphodiesterase treatment, thus demonstrating that M. avium glutamine synthetase was regulated by adenylylation modification.

Characterization of a factor that stimulates hydrolysis of GTP bound to ras gene product p21 (GTPase-activating protein) and correlation of its activity to cell density

1988 ◽  
Vol 8 (10) ◽  
pp. 4169-4173
Author(s):  
M Hoshino ◽  
M Kawakita ◽  
S Hattori
Keyword(s):  
Gene Product ◽  
Cell Density ◽  
Cultured Cells ◽  
Specific Activity ◽  
Gtpase Activating Protein ◽  
Ras Gene ◽  
Cell Extracts ◽  
Mouse Tissues ◽  
Almost All ◽  
Hydrolysis Of

The postmicrosomal fraction of the extract from NIH 3T3 and BALB/c 3T3 cells stimulated the hydrolysis of GTP bound to H-ras gene product p21 by severalfold. The stimulation was observed with normal p21 but not with p21 with valine as the 12th residue. This specificity is similar to that of GTPase-activating protein (GAP) for N-ras p21 described by M. Trahey and F. McCormick (Science 238:542-545, 1987). Consistent with this specificity, analysis of p21-bound nucleotides in living cells revealed that almost all normal p21 bound GDP, whereas oncogenic mutant p21s bound both GTP and GDP. Similar activity was also found in various mouse tissues, with brain tissue showing the highest specific activity. When cell extracts were prepared from cultured cells, there was a linear relationship between GAP activity and cell density. These results suggest the factor is involved in the regulation of cell proliferation.

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 In Vivo Regulation of Glutamine Synthetase Activity in the Marine Chlorophyll b-Containing CyanobacteriumProchlorococcus sp. Strain PCC 9511 (Oxyphotobacteria)

2001 ◽  
Vol 67 (5) ◽  
pp. 2202-2207 ◽  
Author(s):  
Sabah El Alaoui ◽  
Jesús Diez ◽  
Lourdes Humanes ◽  
Fermı́n Toribio ◽  
Frédéric Partensky ◽  
...  
Keyword(s):  
Glutamine Synthetase ◽  
Nitrogen Starvation ◽  
Glutamate Synthase ◽  
Nitrogen Sources ◽  
Synthetase Activity ◽  
Glutamine Synthetase Activity ◽  
Protein Determination ◽  
Physiological Regulation ◽  
Gs Protein

ABSTRACT The physiological regulation of glutamine synthetase (GS; EC6.3.1.2 ) in the axenic Prochlorococcus sp. strain PCC 9511 was studied. GS activity and antigen concentration were measured using the transferase and biosynthetic assays and the electroimmunoassay, respectively. GS activity decreased when cells were subjected to nitrogen starvation or cultured with oxidized nitrogen sources, which proved to be nonusable forProchlorococcus growth. The GS activity in cultures subjected to long-term phosphorus starvation was lower than that in equivalent nitrogen-starved cultures. Azaserine, an inhibitor of glutamate synthase, provoked an increase in enzymatic activity, suggesting that glutamine is not involved in GS regulation. Darkness did not affect GS activity significantly, while the addition of diuron provoked GS inactivation. GS protein determination showed that azaserine induces an increase in the concentration of the enzyme. The unusual responses to darkness and nitrogen starvation could reflect adaptation mechanisms of Prochlorococcus for coping with a light- and nutrient-limited environment.

Exogenous proline application enhances the efficiency of nitrogen fixation and assimilation in chickpea plants exposed to cadmium

2016 ◽  
Author(s):  
Mohammed Nasser Alyemeni ◽  
Qaiser Hayat ◽  
Shamsul Hayat ◽  
Mohammad Faizan ◽  
Ahmad Faraz
Keyword(s):  
Nitrogen Fixation ◽  
Adverse Effects ◽  
Nitrate Reductase ◽  
Glutamine Synthetase ◽  
Glutamate Synthase ◽  
Leaf Nitrogen ◽  
Nitrate Content ◽  
Distilled Water ◽  
Activity Of Enzymes ◽  
Exogenous Proline

Seeds of chickpea were sown in the pots supplemented with 0, 25, 50 or 100 mg of cadmium per kg of soil. At the stage of 30 days after sowing (DAS), the raised plants were sprayed with 20 mM proline except for the control plants which received double distilled water (DDW). The increasing degree of damage caused by the increasing concentration of Cd in soil was partially overcome by proline application. The treatment of 25 mg Cd fed plants with 20 mM proline increased significantly the nodulation parameters, leghemoglobin and carbohydrate content, leaf nitrogen and root nitrate content, activity of enzymes nitrogenase (E.C 1.18.6.1), nitrate reductase (E.C. 1.6.6.1), glutamine synthetase (GS) (E.C 6.3.1.2), glutamate synthase (GOGAT) (E.C 1.4.7.1) and glutamate dehydrogenase (GDH) (E.C 1.4.1.3) over that of the control. The value of these parameters was found to be at par with that of the control in the plants exposed to 50 mg Cd per kg of soil and also treated with 20 mM proline. However, the treatment was not found to be effective in alleviating the adverse effects of 100 mg Cd per kg of soil.

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