<sup>15</sup>N‐NMR studies of nitrogen assimilation and amino acid biosynthesis in the ectomycorrhizal fungus <i>Cenococcum graniforme</i>

Martin, Francis

doi:10.1016/0014-5793(85)80331-8

Cited by 59 publications

(44 citation statements)

References 7 publications

(2 reference statements)

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“…['5N]ammonium incorporation was analyzed using in vivo NMR and GC-MS. Figure 1 Figure 1 is similar to that observed previously by in vivo 5N NMR in the ectomycorrhizal fungus Cenococcum graniforme (12) and shoot-forming cultures of white spruce buds (27 In addition to preventing the incorporation of '5N into amino acids, MSO also affected the concentration of ammonium in the medium (Table III). In control cells the ammonium concentration dropped from 1.6 mm to 0 over 12 h, representing an uptake rate of 1.3 ,umol h-'g fresh wt-'.…”

Section: Results and Discussion Ammonium Assimilationsupporting

confidence: 82%

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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Section: Results and Discussion Ammonium Assimilationsupporting

confidence: 82%

The Role of Glutamate Dehydrogenase in Plant Nitrogen Metabolism

Robinson

Slade²,

Fox³

et al. 1991

Plant Physiol.

284

153

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“…'^N-NMR spectroscopy has proved to have adequate sensitivity and resolution for N assimilation studies in a number of micro-organisms and plant cells (Legerton et al, 1981;Martin, 1985;Robinson et al, 1991 ;Amancio & Santos, 1992;Callies et al, 1992;Fox et al, 1992;Monselise & Kost, 1993). It permits direct monitoring of incorporation of'NH^î nto key metabolites such as glutamate and glutamine, and the incorporation of '''N into the [amino-'•'N]-and [am/(io-'''N]groups of glutamine can be clearly distinguished.…”

Section: Discussionmentioning

confidence: 99%

“…1). The relative concentration of arginine, a long-term N storage compound (Martin, 1985), decreased during rapid growth, whereas glutamine steadily increased. At the same time, the concentration of NH, ' in the medium decreased regularly, reaching ()-5 mM at the beginning of the stationary phase of growth (data not shown).…”

Section: Free Amino Acid Poolsmentioning

confidence: 99%

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NH₄⁺ assimilation in the ectomycorrhizal basidiomycete Laccaria bicolor (Maire) Orton, a ¹⁵N‐NMR study

Martin

Côté

Canet³

1994

New Phytologist

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summary Nuclear magnetic resonance spectroscopy was used to monitor 15NH4+ assimilation and amino acid biosynthesis in the ectomycorrhizal basidiomycete Laccaria bicolor (Maire) Orton. (strain S238). In mycelium growing rapidly on 15NH4+, [amido‐15N]glutamine was the major 15N‐labelled species. When 15N‐labelled mycelium was transferred into medium containing 14NH4+, the resonance for [amino‐15N]glutamine decreased with a half‐life of about 3.0 h, whereas the resonance for [amino‐15N]glutamine remained unchanged. Such behaviour is consistent with glutamine synthetase (GS) being the major route of 15NH4+ assimilation. However, the higher accumulation of [15N]alanine observed in the presence of the GS inhibitor, methionine sulfoximine, indicated that a part of the glutamate pool was formed by the glutamate dehydrogenase (GDH) pathway. When the mycelium was in stationary phase (i.e. low extracellular NH4+), the intramolecular 15N labelling of glutamine suggested that the GDH and GS pathways were simultaneously assimilating NH4+. The N supply and the growth stage, therefore, influence the expression of the activities of GDH and GS. The current isotopic data identify other fates of absorbed 15N: glutamate decarboxylation gives rise to γ‐aminobutyrate; transamination between glutamate and pyruvate yields alanine; and arginine accumulates. It is concluded that GS is the main pathway of primary assimilation of NH4+ in L. bicolor, but GDH may also contribute significantly to this process.

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“…The ratio of glutamine amido-'''N/glutamine amino-''N shows that the label was predominantly incorporated into the amide group of glutamine ( Fig. 6; Martin, 1985). Up to 40",, of the assimilated "N terminated in the amido-N of glutamine.…”

Section: Pathivay Of ''^N Assimilationmentioning

confidence: 96%

The involvement of glutamate dehydrogenase and glutamine synthetase in ammonia assimilation by the rapidly growing ectomycorrhizal ascomycete, Cenococcum geophilum Fr.

Martin¹,

Stewart

Genetet

et al. 1988

New Phytologist

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SUMMARYIn order to detern-iine signifieance oi ti-ie glutamate cieiiycirogenase pathvvav-aiui a glutamine svnthetase/glutamate synthase cycle in NH,^assimilation, we followed a t-itit-i-iher of different metholic parameters (nutrient uptake, free amino acid pools, NH|*-indueed glutamine acetimuhnion) and ''"N incorporation into an-iino acids of rapidly growing Ceiioeorciiiii geophiluin. .Arginine was a major free amino aeid in C. neopliiliiiti during its entire growth period, C. /^eophihiiii synthesized and aeeumulated very iarge an-iout-its of gliitan-iine at the heginning of tiie rapid phase of growth in low nitrogen mediun-i, ciuring the wiioie growth period in high nitrogen medium, anti immediately after addition of NH,', Therefore, the accumulation of a large an-iount of glutatnine took place when the external ammoniut-i-i concentration was high. The current data identify four pathways of N n-ietaholism in rapidly growing C. geophiluiir. (1) glutamine synthesis, involving transfer of N to hoth an-iino and amido moieties;(2) glutamate formation; (.3) transamination with pyruvate to yield aianine; (4) transamination with oxaioaeetate to yield asparate. The higher accumulation oi glutan-iate anti related ammo acitis (alanine and asparlate) in the presence of the glutamine svnthetase inhii>itor methionine sulpiioximine indicates that giutamate, the precursor of glutamine, was formed hy a pathway insensitive to methionine sulphoximine, the glutan-iate dehydrogenase pathway. Up to 40",, of the assimilated '''N terminated in the at-i-iido-N of glutamine. These data are eonsistent with a piv-otal role for glutan-iine synthetase activity and indicates that the primary assimilation of Nll,^ in rapidly growing C. geopliiliiiii is brought ahout hy coiKurrent activitv-of the (il)ll ai-iti (IS pathways. The patiiwav-of primary assimilation of NH ,* hy ('. geophituiii in the rapid phase of growth therefore differs fron-i those operating in the stationary phase of growth where N Hux through (JDH is higher than the flux through the GS pathway.

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¹⁵N‐NMR studies of nitrogen assimilation and amino acid biosynthesis in the ectomycorrhizal fungus Cenococcum graniforme

Cited by 59 publications

References 7 publications

The Role of Glutamate Dehydrogenase in Plant Nitrogen Metabolism

The Role of Glutamate Dehydrogenase in Plant Nitrogen Metabolism

NH₄⁺ assimilation in the ectomycorrhizal basidiomycete Laccaria bicolor (Maire) Orton, a ¹⁵N‐NMR study

The involvement of glutamate dehydrogenase and glutamine synthetase in ammonia assimilation by the rapidly growing ectomycorrhizal ascomycete, Cenococcum geophilum Fr.

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15N‐NMR studies of nitrogen assimilation and amino acid biosynthesis in the ectomycorrhizal fungus Cenococcum graniforme

Cited by 59 publications

References 7 publications

The Role of Glutamate Dehydrogenase in Plant Nitrogen Metabolism

The Role of Glutamate Dehydrogenase in Plant Nitrogen Metabolism

NH4+ assimilation in the ectomycorrhizal basidiomycete Laccaria bicolor (Maire) Orton, a 15N‐NMR study

The involvement of glutamate dehydrogenase and glutamine synthetase in ammonia assimilation by the rapidly growing ectomycorrhizal ascomycete, Cenococcum geophilum Fr.

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¹⁵N‐NMR studies of nitrogen assimilation and amino acid biosynthesis in the ectomycorrhizal fungus Cenococcum graniforme

NH₄⁺ assimilation in the ectomycorrhizal basidiomycete Laccaria bicolor (Maire) Orton, a ¹⁵N‐NMR study