scholarly journals Regulation of synthesis of glutamate dehydrogenase and glutamine synthetase in micro-organisms

1969 ◽  
Vol 115 (4) ◽  
pp. 769-775 ◽  
Author(s):  
J. A. Pateman
Keyword(s):  
Escherichia Coli ◽  
Glutamine Synthetase ◽  
Glutamate Dehydrogenase ◽  
Nitrogen Sources ◽  
Sole Source ◽  
Synthetase Activity ◽  
Glutamine Synthetase Activity ◽  
Escherichia Coli Cells ◽  
High Concentrations ◽  
Micro Organisms

1. Aspergillus nidulans, Neurospora crassa and Escherichia coli were grown on media containing a range of concentrations of nitrate, or ammonia, or urea, or l-glutamate, or l-glutamine as the sole source of nitrogen and the glutamate dehydrogenate and glutamine synthetase of the cells measured. 2. Aspergillus, Neurospora and Escherichia coli cells, grown on l-glutamate or on high concentrations of ammonia or on high concentrations of urea, possessed low glutamate dehydrogenase activity compared with cells grown on other nitrogen sources. 3. Aspergillus, Neurospora and Escherichia coli cells grown on l-glutamate possessed high glutamine synthetase activity compared with cells grown on other nitrogen sources. 4. The hypothesis is proposed that in Aspergillus, Neurospora and Escherichia colil-glutamate represses the synthesis of glutamate dehydrogenase and l-glutamine represses the synthesis of glutamine synthetase. 5. A comparison of the glutamine-synthesizing activity and the γ-glutamyltransferase activity of glutamine synthetase in Aspergillus and Neurospora gave no indication that these fungi produce different forms of glutamine synthetase when grown on ammonia or l-glutamate as nitrogen sources.

scholarly journals NITROGEN NUTRITION AND SEEDLING DEVELOPMENT OF NORMAL AND OPAQUE-2 MAIZE GENOTYPES

1984 ◽  
Vol 64 (4) ◽  
pp. 885-894 ◽  
Author(s):  
SANGITA HANDA ◽  
H. L. WARREN ◽  
D. M. HUBER ◽  
C. Y. TSAI
Keyword(s):  
Glutamine Synthetase ◽  
Glutamate Dehydrogenase ◽  
Nitrogen Nutrition ◽  
Dry Weight ◽  
Synthetase Activity ◽  
Glutamine Synthetase Activity ◽  
Glutamate Dehydrogenase Activity ◽  
Early Seedling ◽  
High Concentrations ◽  
Normal Genotype

Early seedling growth and glutamine synthetase and glutamate dehydrogenase activities of the normal and opague-2 (o2) genotypes of maize were compared in the presence or absence of added N. In the absence of exogenous N, the dry weight of o2 seedlings was only 60% of the dry weight of normal seedlings at 21 days after germination; however, the dry weights were comparable when exogenous N, especially as NO−3, was supplied to both genotypes. Thus, exogenous N appears to be more critical for early growth of o2 than normal seedlings. Growth of o2 seedlings was more severely restricted than of the normal genotype by high concentrations of NH+4. A combination of NH+4 and NO−3 resulted in better growth of both genotypes than either form on N alone. There was no difference in the capacity of the two genotypes to accumulate N from exogenous NH+4 or NO−3. However, both genotypes accumulated relatively more N from NH+4 than from NO−3. Glutamine synthetase activity in o2 roots was twofold higher than in the normal genotype in the absence of exogenous N but was similar in the roots of both gentoypes when seedlings were grown in either NO−3 or NH+4. In the absence of exogenous N, glutamate dehydrogenase activity in o2 roots was 2.8-fold higher than in normal roots and remained higher when NH+4 was added.Key words: Nitrogen form, ammonium, nitrate, glutamate dehydrogenase, glutamine synthetase, zein

Regulation of ammonia-assimilating enzymes by various nitrogen sources in cultured Ipomoea spp.

1989 ◽  
Vol 67 (11) ◽  
pp. 3127-3133 ◽  
Author(s):  
M. W. Zink
Keyword(s):  
Glutamine Synthetase ◽  
Glutamate Dehydrogenase ◽  
Growth Medium ◽  
Glutamate Synthase ◽  
Nitrogen Sources ◽  
Defined Medium ◽  
Morning Glory ◽  
Synthetase Activity ◽  
Glutamine Synthetase Activity ◽  
Chemically Defined Medium

The levels of ammonia-assimilating enzymes of Ipomoea spp. (morning glory) grown in suspension culture on a chemically defined medium are affected by various nitrogen sources. An increase in nitrate or ammonium concentrations in the growth medium elevated the levels of glutamate dehydrogenase, glutamine synthetase, and glutamate synthase. The levels of the enzymes varied in a manner similar to the growth pattern of the cells. When the growth rate of Ipomoea was maximal, high levels of enzymes were obtained; when cell growth was poor, a low yield of enzymes was obtained. Glutamine, whether used as the sole nitrogen source or as a supplement in media containing ammonium plus nitrate, increased the level of glutamate dehydrogenase and decreased the level of the other two enzymes. The developmental pattern of glutamine synthetase activity with culture age in Ipomoea differed with different nitrogen sources in the growth medium.

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.

Cellular regulation of glutamine synthetase activity in Escherichia coli

1968 ◽  
Vol 6 ◽  
pp. 257-289 ◽  
Author(s):  
E.R. Stadtman ◽  
B.M. Shapiro ◽  
H.S. Kingdon ◽  
C.A. Woolfolk ◽  
J.S. Hubbard
Keyword(s):  
Escherichia Coli ◽  
Glutamine Synthetase ◽  
Synthetase Activity ◽  
Glutamine Synthetase Activity ◽  
Cellular Regulation

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 Submitochondrial localization and function of enzymes of glutamine metabolism in avian liver.

1977 ◽  
Vol 73 (2) ◽  
pp. 300-310 ◽  
Author(s):  
J E Vorhaben ◽  
J W Campbell
Keyword(s):  
Glutamine Synthetase ◽  
Glutamate Dehydrogenase ◽  
Liver Mitochondria ◽  
Glutamine Metabolism ◽  
Synthetase Activity ◽  
Glutamine Synthetase Activity ◽  
The Matrix ◽  
Matrix Compartment ◽  
Matrix Fraction ◽  
And Function

Glutamine synthetase (EC 6.3.1.2) was localized within the matrix compartment of avian liver mitochondria. The submitochondrial localization of this enzyme was determined by the digitonin-Lubrol method of Schnaitman and Greenawalt (35). The matrix fraction contained over 74% of the glutamine synthetase activity and the major proportion of the matirx marker enzymes, malate dehydrogenase (71%), NADP-dependent isocitrate dehydrogenase (83%), and glutamate dehydrogenase (57%). The highest specific activities of these enzymes were also found in the matrix compartment. Oxidation of glutamine by avian liver mitochondria was substantially less than that of glutamate. Bromofuroate, an inhibitor of glutamate dehydrogenase, blocked oxidation of glutamate and of glutamine whereas aminoxyacetate, a transaminase inhibitor, had little or no effect with either substrate. These results indicate that glutamine metabolism is probably initiated by the conversion of glutamine to glutamate rather than to an alpha-keto acid. The localization of a glutaminase activity within avian liver mitochondria plus the absence of an active mitochondrial glutamine transaminase is consistent with the differential effects of the transaminase and glutamate dehydrogenase inhibitors. The high glutamine synthetase activity (40:1) suggests that mitochondrial catabolism of glutamine is minimal, freeing most of the glutamine synthesized for purine (uric acid) biosynthesis.

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