Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:1.4.1.2 (glutamate dehydrogenase)
4,380 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Illuminated pea (Pisum sativum) chloroplasts catalyze (ammonia plus alpha-ketoglutarate [alpha-KG])-dependent O(2) evolution at rates which are commensurate with other estimates of the flux of assimilated nitrogen (mean of eight determinations, 8.3 mumole per mg chlorophyll per hour, sd 2.4). The reaction was usually initiated with 1 mm ammonia after preincubating chloroplasts in the presence of alpha-KG, ADP, pyrophosphate, and MgCl(2).Progressive increases in ammonia concentration gave V(max)/2 at 0.2 mm (approximately) and V(max) at about 1 mm. Higher concentrations were inhibitory; at 7 mm the rate was again about V(max)/2. The highest ratio of O(2) evolved per mol of ammonia supplied was 0.36.The (ammonia plus alpha-KG)-dependent reaction was inhibited by methionine sulfoximine, azaserine, and aspartate in the presence of amino-oxyacetate but not by amino-oxyacetate alone and not by l-glutamate. The rate of O(2) evolution in the presence of 1 mm ammonia and 2.5 mm alpha-KG was increased only slightly by addition of 5 mm glutamine. Similarly, the rate of O(2) evolution in the presence of 5 mm glutamine and 2.5 mm alpha-KG was increased only slightly by addition of 1 mm ammonia.The results are attributed to the incorporation of ammonia via glutamine synthetase and reductive transamination of the glutamine formed by photosynthetically coupled glutamate synthase using alpha-KG as the amino acceptor. Several lines of evidence rule out the possibility that photosynthetically coupled glutamate dehydrogenase is involved.
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PMID:Polarographic study of ammonia assimilation by isolated chloroplasts. 1666 Jan 25

Two hours after the addition of l-methionine-dl-sulfoximine to the cell suspension, glutamine synthetase activity was inhibited by more than 90% in air-grown Chlamydomonas reinhardii. Cells continued to take up NH(3) from the medium provided that the concentration of dissolved CO(2) was high (equilibrated with 4% CO(2) in air). This NH(3) uptake, about 30% of the control, is discussed in terms of glutamate dehydrogenase activity. Without CO(2), or with a low CO(2) level, a NH(3) excretion was observed, the rate of which depended on the actual concentration of the dissolved CO(2). Experiments with (15)NH(3) demonstrated that no NH(3) uptake was masked by this excretion and inversely that no excretion occurred during the uptake in the conditions where it took place. Furthermore, the NH(3) excretion observed in the absence of CO(2) increased when O(2) concentration rose to 15% and was inhibited when 10 millimolar isonicotinic acid hydrazide was supplied to the algal suspension. Thus, NH(3) excretion in the presence of l-methionine-dl-sulfoximine seems to be related to a photorespiratory process inasmuch as it presents the same properties with regard to the O(2) and the isonicotinic acid hydrazide effects. These results favor the hypothesis that NH(3) produced in the medium originates from the glycine to serine reaction. On the other hand, partial inhibition (50%) of photosynthesis by l-methionine-dl-sulfoximine was attributed to uncoupling between electron transfer and photophosphorylation due to NH(3) accumulation into the cell.
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PMID:Ammonia exchange and photorespiration in chlamydomonas. 1666 24

Ammonium assimilation was followed in N-starved mycelia from the ectomycorrhizal Ascomycete Cenococcum graniforme. The evaluation of free amino acid pool levels after the addition of 5 millimolar NH(4) (+) indicated that the absorbed ammonium was assimilated rapidly. Post-feeding nitrogen content of amino acids was very different from the initial values. After 8 hours of NH(4) (+) feeding, glutamine accounted for the largest percentage of free amino acid nitrogen (43%). The addition of 5 millimolar methionine sulfoximine (MSX) to NH(4) (+)-fed mycelia caused an inhibition of glutamine accumulation with a corresponding increase in glutamate and alanine levels.Using (15)N as a tracer, it was found that the greatest initial labeling was into glutamine and glutamate followed by aspartate, alanine, and ornithine. On inhibiting glutamine synthetase using MSX, (15)N enrichment of glutamate, alanine, aspartate, and ornithine continued although labeling of glutamine was quite low. Moreover, the incorporation of (15)N label in insoluble nitrogenous compounds was lower in the presence of MSX. From the composition of free amino acid pools, the (15)N labeling pattern and effects of MSX, NH(4) (+) assimilation in C. graniforme mycelia appears to proceed via glutamate dehydrogenase pathway. This study also demonstrates that glutamine synthesis is an important reaction of ammonia utilization.
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PMID:Nitrogen Assimilation in Mycorrhizas : Ammonium Assimilation in the N-Starved Ectomycorrhizal Fungus Cenococcum graniforme. 1666 52

Stichococcus bacillaris Naeg., a green soil alga, can grow in the presence of methionine sulfoximine (MSX), an inhibitor of glutamine synthetase, by maintaining a high level of NADPH-glutamate dehydrogenase activity. MSX-grown cells can utilize both NH(4) (+) and NO(3) (-) as nitrogen source for growth. [(14)C]Methylammonium is not metabolized by S. bacillaris, and is transported by a carrier system that obeys Michaelis Menten kinetics, and is insensitive to MSX.
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PMID:Transport and Assimilation of Nitrogen by Stichococcus bacillaris Grown in the Presence of Methionine Sulfoximine. 1666 42

Succulent stems of Cissus quadrangularis L. (Vitaceae) contain glutamine synthetase, glutamate synthase, and glutamate dehydrogenase. The CO(2) and water gas exchanges of detached internodes were typical for Crassulacean acid metabolism plants. During three physiological phases, e.g. in the dark, in the early illumination period after stomata closure, and during the late light phase with the stomata wide open, (15)NH(4)Cl was injected into the central pith of stem sections. The kinetics of (15)N labeling in glutamate and glutamine suggested that glutamine synthetase was involved in the initial ammonia fixation. In the presence of methionine sulfoximine, an inhibitor of glutamine synthetase, the incorporation of (15)N derived from (15)NH(4)Cl was almost completely inhibited. Injections of amido-(15)N glutamine demonstrated a potential for (15)N transfer from the amido group of glutamine into glutamate which was suppressed by the glutamate synthase inhibitor, azaserine. The evidence indicates that glutamine synthetase and glutamate synthase could assimilate ammonia and cycle nitrogen during all phases of Crassulacean acid metabolism.
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PMID:Ammonia Fixation via Glutamine Synthetase and Glutamate Synthase in the CAM Plant Cissus quadrangularis L. 1666 20

When Lemna minor L. is supplied with the potent inhibitor of glutamine synthetase, methionine sulfoximine, rapid changes in free amino acid levels occur. Glutamine, glutamate, asparagine, aspartate, alanine, and serine levels decline concomitantly with ammonia accumulation. However, not all free amino acid pools deplete in response to this inhibitor. Several free amino acids including proline, valine, leucine, isoleucine, threonine, lysine, phenylalanine, tyrosine, histidine, and methionine exhibit severalfold accumulations within 24 hours of methionine sulfoximine treatment. To investigate whether these latter amino acid accumulations result from de novo synthesis via a methionine sulfoximine insensitive pathway of ammonia assimilation (e.g. glutamate dehydrogenase) or from protein turnover, fronds of Lemna minor were prelabeled with [(15)N]H(4) (+) prior to supplying the inhibitor. Analyses of the (15)N abundance of free amino acids suggest that protein turnover is the major source of these methionine sulfoximine induced amino acid accumulations. Thus, the pools of valine, leucine, isoleucine, proline, and threonine accumulated in response to the inhibitor in the presence of [(15)N]H(4) (+), are (14)N enriched and are not apparently derived from (15)N-labeled precursors. To account for the selective accumulation of amino acids, such as valine, leucine, isoleucine, proline, and threonine, it is necessary to envisage that these free amino acids are relatively poorly catabolized in vivo. The amino acids which deplete in response to methionine sulfoximine (i.e. glutamate, glutamine, alanine, aspartate, asparagine, and serine) are all presumably rapidly catabolized to ammonia, either in the photorespiratory pathway or by alternative routes.
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PMID:Amino Acid Metabolism of Lemna minor L. : I. Responses to Methionine Sulfoximine. 1666 34

Ammonia production and assimilation(1) were examined in photorespiratory mutants of Arabidopsis thaliana L. lacking ferredoxin-dependent glutamate synthase (Fd-GluS) activity. Although photosynthesis was rapidly inhibited in these mutants in normal air, NH(4) (+) continued to accumulate. The accumulation of NH(4) (+) was also seen after an initial lag of 30 minutes in 2% O(2), 350 microliters per liter of CO(2) and after 90 minutes in 2% O(2), 900 microliters per liter of CO(2). The accumulation of NH(4) (+) in normal air and low O(2) was also associated with an increase in the total pool of amino acid-N and glutamine, and a decrease in the pools of glutamate, aspartate, alanine, and serine. Upon return to dark conditions, or to 21% O(2), 1% CO(2) in the light, the NH(4) (+) which had accumulated in the leaves was reassimilated into amino acids. The addition of methionine sulfoximine (MSO) resulted in higher accumulations of NH(4) (+) in glutamate synthase mutants and prevented the reassimilation of NH(4) (+) upon return to the dark. The addition of MSO also resulted in the accumulation of NH(4) (+) in glutamate synthase mutants in the light and in 21% O(2), 1% CO(2). These results indicate that glutamine synthetase is essential for the reassimilation of photorespiratory NH(4) (+) and for primary N assimilation in the leaves and strongly suggest that glutamate dehydrogenase plays only a minimal role in the assimilation of ammonia. Levels of NADH-dependent glutamate synthase (NADH-GluS) appear to be sufficient to account for the assimilation of NH(4) (+) by a GS/NADH-GluS cycle.
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PMID:Ammonia Production and Assimilation in Glutamate Synthase Mutants of Arabidopsis thaliana. 1666 91

Chlorella autotrophica, a euryhaline marine alga, and Stichococcus bacillaris, a salt-tolerant soil alga, grow in the presence of methionine sulfoximine (MSX), an inhibitor of glutamine synthetase, by maintaining high levels of NADPH-glutamate dehydrogenase. Nitrate reductase showed no change in MSX-adapted cells. For both species, MSX-adapted cells retained their capacity to accumulate proline in response to salinity, and in S. bacillaris no major shift was observed in the presence of MSX toward the accumulation of sorbitol. Following transfer from 33 to 150% artificial seawater (ASW), both algae exhibited increases in organic solute levels without a lag. Within 6 h of this sudden increase in salinity, the levels of proline in C. autotrophica and of proline and sorbitol in S. bacillaris were similar to those found in steady state 150% ASW cultures. Following transfer from 33 to 150% ASW, S. bacillaris continued [(14)C] bicarbonate photoassimilation at a normal rate and maintained active enzymes of nitrogen assimilation. The incorporation of [(14)C]phenylalanine into proteins was inhibited for about 30 minutes in MSX-free cells and 90 minutes in MSX-adapted cells following transfer from 33 to 150% ASW; the recovery after these lag periods was almost complete.
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PMID:The Relationship between Inorganic Nitrogen Metabolism and Proline Accumulation in Osmoregulatory Responses of Two Euryhaline Microalgae. 1666 6

In higher plants it is now generally considered that glutamate dehydrogenase (GDH) plays only a small or negligible role in ammonia assimilation. To test this specific point, comparative studies of (15)NH(4) (+) assimilation were undertaken with a GDH1-null mutant of Zea mays and a related (but not strictly isogenic) GDH1-positive wild type from which this mutant was derived. The kinetics of (15)NH(4) (+) assimilation into free amino acids and total reduced nitrogen were monitored in both roots and shoots of 2-week-old seedlings supplied with 5 millimolar 99% ((15)NH(4))(2)SO(4) via the aerated root medium in hydroponic culture over a 24-h period. The GDH1-null mutant, with a 10- to 15-fold lower total root GDH activity in comparison to the wild type, was found to exhibit a 40 to 50% lower rate of (15)NH(4) (+) assimilation into total reduced nitrogen. Observed rates of root ammonium assimilation were 5.9 and 3.1 micromoles per hour per gram fresh weight for the wild type and mutant, respectively. The lower rate of (15)NH(4) (+) assimilation in the mutant was associated with lower rates of labeling of several free amino acids (including glutamate, glutamine-amino N, aspartate, asparagine-amino N, and alanine) in both roots and shoots of the mutant in comparison to the wild type. Qualitatively, these labeling kinetics appear consistent with a reduced flux of (15)N via glutamate in the GDH1-null mutant. However, the responses of the two genotypes to the potent inhibitor of glutamine synthetase, methionine sulfoximine, and differences in morphology of the two genotypes (particularly a lower shoot:root ratio in the GDH1-null mutant) urge caution in concluding that GDH1 is solely responsible for these differences in ammonia assimilation rate.
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PMID:Kinetics of NH(4) Assimilation in Zea mays: Preliminary Studies with a Glutamate Dehydrogenase (GDH1) Null Mutant. 1666 61

The subcellular distribution of l-glutamate dehydrogenase (GDH, EC 1.4.1.3.) was studied in SB3 soybean (Glycine max) cells using subcellular fractionation techniques. Compounds that inhibit protein synthesis either on 80s or 70s ribosomes were also used to give a preliminary idea of which subcellular fraction is involved in GDH synthesis. It was found that whereas cycloheximide and puromycin considerably reduced the total amount of protein synthesized by the cells, they did not appear to inhibit the synthesis of GDH. In the presence of chloramphenicol, both GDH activity and protein level in the cells were considerably reduced, suggesting that this enzyme was synthesized in organelles and not in the cytosol. Streptomycin, which inhibits plastid protein synthesis, also inhibited synthesis of GDH, indicating that a fraction of GDH activity was plastidial in origin. This is supported by the data on subcellular distribution of the enzyme, which showed that a major fraction of GDH is found in the plastidial fraction, although some activity is found associated with the mitochondrial fraction also. Since a major fraction of GDH activity was found in the plastidial fraction, we studied protein synthesis using isolated plastids and (35)S-methionine. Using antibodies raised against purified GDH, we identified a (35)S-labeled 41-kilodalton polypeptide synthesized by plastids as GDH.
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PMID:A Plastidial Localization and Origin of l-Glutamate Dehydrogenase in a Soybean Cell Culture. 1666 61


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