Assimilation Of Ammonia by Glutamate Dehydrogenase?

Rhodes, David; Brunk, Dennis G.; Magalhães, J. R.

doi:10.1007/978-1-4613-0835-5_6

Cited by 26 publications

(25 citation statements)

References 36 publications

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“…There are reports of relatively small amounts of incorporation via an MSO insensitive pathway (18), but these represent less than 1% of total ammonium incorporated. Assuming that MSO does not affect the activity ofGDH, and this assumption has been questioned (18), the general conclusion from these experiments is that GDH plays no role in ammonium assimilation. The present investigation was undertaken to establish if the function of GDH is the catabolism of glutamate.…”

mentioning

confidence: 99%

“…complementary role to the GOGAT cycle (18,23,29). Alternatively, it could catalyze the oxidation of glutamate and furnish carbon to the TCA cycle (26).…”

mentioning

confidence: 99%

“…Inhibition of GS by MSO brings about an accumulation of ammonium and stops the incorporation of '5N-labeled ammonium into amino acids (2,6,20). There are reports of relatively small amounts of incorporation via an MSO insensitive pathway (18), but these represent less than 1% of total ammonium incorporated. Assuming that MSO does not affect the activity ofGDH, and this assumption has been questioned (18), the general conclusion from these experiments is that GDH plays no role in ammonium assimilation.…”

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confidence: 99%

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The Role of Glutamate Dehydrogenase in Plant Nitrogen Metabolism

Robinson

Slade²,

Fox³

et al. 1991

Plant Physiol.

284

153

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In vivo nuclear magnetic resonance spectroscopy, in vitro gas chromatography-mass spectrometry, and automated 15N/13C mass spectrometry have been used to demonstrate that glutamate dehydrogenase is active in the oxidation of glutamate, but not in the reductive amination of 2-oxoglutarate. In cell suspension cultures of carrot (Daucus carota L. cv Chantenay), primary assimilation of ammonium occurs via the glutamate synthase pathway. Glutamate dehydrogenase is derepressed in carbonlimited cells and in such cells the function of glutamate dehydrogenase appears to be the oxidation of glutamate, thus ensuring sufficient carbon skeletons for effective functioning of the tricarboxylic acid cycle. This catabolic role for glutamate dehydrogenase implies an important regulatory function in carbon and nitrogen metabolism.

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confidence: 99%

“…complementary role to the GOGAT cycle (18,23,29). Alternatively, it could catalyze the oxidation of glutamate and furnish carbon to the TCA cycle (26).…”

mentioning

confidence: 99%

mentioning

confidence: 99%

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The Role of Glutamate Dehydrogenase in Plant Nitrogen Metabolism

Robinson

Slade²,

Fox³

et al. 1991

Plant Physiol.

284

153

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“…Conversely, if GDH operates in the catabolic direction, it may help alter cellular C to N ratios and/or fuel the TCA cycle under conditions of C deficit (Rhodes et al, 1989;Robinson et al, 1991Robinson et al, , 1992Aubert et al, 2001;Loulakakis and RoubelakisAngelakis, 2001;Miflin and Habash, 2002;Dubois et al, 2003;Skopelitis et al, 2006).…”

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confidence: 99%

Tobacco Isoenzyme 1 of NAD(H)-Dependent Glutamate Dehydrogenase Catabolizes Glutamate in Vivo

Purnell

Botella

2006

Plant Physiol.

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Glutamate (Glu) dehydrogenase (GDH, EC 1.4.1.2-1.4.1.4) catalyzes in vitro the reversible amination of 2-oxoglutarate to Glu. The in vivo direction(s) of the GDH reaction in higher plants and hence the role(s) of this enzyme is unclear, a situation confounded by the existence of isoenzymes comprised totally of either GDH b-(isoenzyme 1) or a-(isoenzyme 7) subunits, as well as another five a-b isoenzyme permutations. To clarify the in vivo direction of the reaction catalyzed by GDH isoenzyme 1, [ 15 N]Glu was supplied to roots of two independent transgenic tobacco (Nicotiana tabacum) lines with increased isoenzyme 1 levels (S4-H and S49-H). The [ 15 N]ammonium (NH 4 1 ) accumulation rate in these lines was elevated approximately 65% compared with a null segregant control line, indicating that isoenzyme 1 catabolizes Glu in roots. Leaf glutamine synthetase (GS) was inhibited with a GS-specific herbicide to quantify any contribution by GDH toward photorespiratory NH 4 1 reassimilation. Transgenic line S49-H did not show enhanced resistance to the herbicide, indicating that the large pool of isoenzyme 1 in S49-H leaves was unable to compensate for GS and suggesting that isoenzyme 1 does not assimilate NH 4 1 in vivo.The intricate linkage of plant C and N metabolism requires constant balancing at the cellular level. Fundamentally, this involves orchestrating cellular levels of three metabolites: ammonium (NH 4

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“…These results support the earlier findings of Wallsgrove et al (1987), which suggested that GS/GOGAT played a key role in the reassimilation of ammonia released during photorespiration. However, GDH may play a complementary role to GS/GOGAT in the reassimilation of excess ammonia released during stress conditions or during specific stages of development (Yamaya et al, 1986;Rhodes et al, 1989; for review, see Stewart et al, 1980;Srivastava and Singh, 1987).…”

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Characterization and Expression of NAD(H)-Dependent Glutamate Dehydrogenase Genes in Arabidopsis

et al. 1997

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Two distinct cDNA clones encoding NAD(H)-dependent glutamate dehydrogenase (NAD[H]-GDH) in Arabidopsis thaliana were identified and sequenced. The genes corresponding to these cDNA clones were designated GDH1 and GDH2. Analysis of the deduced amino acid sequences suggest that both gene products contain putative mitochondrial transit polypeptides and NAD(H)- and α--ketoglutarate-binding domains. Subcellular fractionation confirmed the mitochondrial location of the NAD(H)-GDH isoenzymes. In addition, a putative EF-hand loop, shown to be associated with Ca2+ binding, was identified in the GDH2 gene product but not in the GDH1 gene product. GDH1 encodes a 43.0-kD polypeptide, designated α-, and GDH2 encodes a 42.5-kD polypeptide, designated [beta]. The two subunits combine in different ratios to form seven NAD(H)-GDH isoenzymes. The slowest-migrating isoenzyme in a native gel, GDH1, is a homohexamer composed of α- subunits, and the fastest-migrating isoenzyme, GDH7, is a homohexamer composed of [beta] subunits. GDH isoenzymes 2 through 6 are heterohexamers composed of different ratios of α- and [beta] subunits. NAD(H)-GDH isoenzyme patterns varied among different plant organs and in leaves of plants irrigated with different nitrogen sources or subjected to darkness for 4 d. Conversely, there were little or no measurable changes in isoenzyme patterns in roots of plants treated with different nitrogen sources. In most instances, changes in isoenzyme patterns were correlated with relative differences in the level of α- and [beta] subunits. Likewise, the relative difference in the level of α- or [beta] subunits was correlated with changes in the level of GDH1 or GDH2 transcript detected in each sample, suggesting that NAD(H)-GDH activity is controlled at least in part at the transcriptional level.

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Assimilation Of Ammonia by Glutamate Dehydrogenase?

Cited by 26 publications

References 36 publications

The Role of Glutamate Dehydrogenase in Plant Nitrogen Metabolism

The Role of Glutamate Dehydrogenase in Plant Nitrogen Metabolism

Tobacco Isoenzyme 1 of NAD(H)-Dependent Glutamate Dehydrogenase Catabolizes Glutamate in Vivo

Characterization and Expression of NAD(H)-Dependent Glutamate Dehydrogenase Genes in Arabidopsis

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