scholarly journals The regulation of activity of the enzymes involved in the assimilation of nitrate by higher plants

1966 ◽  
Vol 100 (3) ◽  
pp. 577-588 ◽  
Author(s):  
J Ingle ◽  
K W Joy ◽  
R H Hageman
Keyword(s):  
Nitrate Reductase ◽  
Glutamate Dehydrogenase ◽  
Nitrite Reductase ◽  
Actinomycin D ◽  
Higher Plants ◽  
Specific Inhibitor ◽  
Nitrate Assimilation ◽  
End Products ◽  
Regulation Of Activity

1. Possible mechanisms regulating the activities of three enzymes involved in nitrate assimilation, nitrate reductase, nitrite reductase and glutamate dehydrogenase, were studied in radish cotyledons. 2. Nitrate-reductase and nitrite-reductase activities are low in nitrogen-deficient cotyledons, and are induced by their substrates. 3. Glutamate dehydrogenase is present regardless of the nitrogen status, and the enzyme can be increased only slightly by long-term growth on ammonia. 4. Although nitrate is the best inducer of nitrate reductase, lower levels of induction are also obtained with nitrite and ammonia. The experiments did not distinguish between direct or indirect induction by these two molecules. 5. Nitrite reductase is induced by nitrite and only indirectly by nitrate. 6. The induction of both nitrate reductase and nitrite reductase is prevented by the inhibitors actinomycin D, puromycin and cycloheximide, indicating a requirement for the synthesis of RNA and protein. 7. The decay of nitrate reductase, determined after inhibition of protein synthesis, is slower than the synthesis of the enzyme. Nitrite reductase is much more stable than nitrate reductase. 8. The synthesis of nitrate reductase is not repressed by ammonia, but is repressed by growth on a nitrite medium. 9. There is no inhibition of nitrate reductase, nitrite reductase or glutamate dehydrogenase by the normal end products of assimilation, but cyanate is a fairly specific inhibitor of nitrate reductase.

Nitrate reductase, nitrite reductase and glutamate dehydrogenase levels in roots and leaves of maize seedlings

1976 ◽  
Vol 18 (4) ◽  
pp. 283-289 ◽  
Author(s):  
Tatiana Pšenáková ◽  
Otília Gašparíková ◽  
Anna Nižňanská
Keyword(s):  
Nitrate Reductase ◽  
Glutamate Dehydrogenase ◽  
Nitrite Reductase ◽  
Maize Seedlings

scholarly journals Induction of the Nitrate AssimilationnirAOperon and Protein-Protein Interactions in the Maturation of Nitrate and Nitrite Reductases in the Cyanobacterium Anabaena sp. Strain PCC 7120

2015 ◽  
Vol 197 (14) ◽  
pp. 2442-2452 ◽  
Author(s):  
José E. Frías ◽  
Enrique Flores
Keyword(s):  
Nitrate Reductase ◽  
Protein Interactions ◽  
Nitrite Reductase ◽  
Nitrate Assimilation ◽  
Protein Protein Interactions ◽  
Content Type ◽  
Nitrite Reductases ◽  
Nitrate And Nitrite ◽  
Pcc 7120 ◽  
Assimilation System

ABSTRACTNitrate is widely used as a nitrogen source by cyanobacteria, in which the nitrate assimilation structural genes frequently constitute the so-callednirAoperon. This operon contains the genes encoding nitrite reductase (nirA), a nitrate/nitrite transporter (frequently an ABC-type transporter;nrtABCD), and nitrate reductase (narB). In the model filamentous cyanobacteriumAnabaenasp. strain PCC 7120, which can fix N2in specialized cells termed heterocysts, thenirAoperon is expressed at high levels only in media containing nitrate or nitrite and lacking ammonium, a preferred nitrogen source. Here we examined the genes downstream of thenirAoperon inAnabaenaand found that a small open reading frame of unknown function,alr0613, can be cotranscribed with the operon. The next gene in the genome,alr0614(narM), showed an expression pattern similar to that of thenirAoperon, implying correlated expression ofnarMand the operon. A mutant ofnarMwith an insertion mutation failed to produce nitrate reductase activity, consistent with the idea that NarM is required for the maturation of NarB. BothnarMandnarBmutants were impaired in the nitrate-dependent induction of thenirAoperon, suggesting that nitrite is an inducer of the operon inAnabaena. It has previously been shown that the nitrite reductase protein NirA requires NirB, a protein likely involved in protein-protein interactions, to attain maximum activity. Bacterial two-hybrid analysis confirmed possible NirA-NirB and NarB-NarM interactions, suggesting that the development of both nitrite reductase and nitrate reductase activities in cyanobacteria involves physical interaction of the corresponding enzymes with their cognate partners, NirB and NarM, respectively.IMPORTANCENitrate is an important source of nitrogen for many microorganisms that is utilized through the nitrate assimilation system, which includes nitrate/nitrite membrane transporters and the nitrate and nitrite reductases. Many cyanobacteria assimilate nitrate, but regulation of the nitrate assimilation system varies in different cyanobacterial groups. In the N2-fixing, heterocyst-forming cyanobacteria, thenirAoperon, which includes the structural genes for the nitrate assimilation system, is expressed in the presence of nitrate or nitrite if ammonium is not available to the cells. Here we studied the genes required for production of an active nitrate reductase, providing information on the nitrate-dependent induction of the operon, and found evidence for possible protein-protein interactions in the maturation of nitrate reductase and nitrite reductase.

scholarly journals The roles of the nitrate reductase NarGHJI, the nitrite reductase NirBD and the response regulator GlnR in nitrate assimilation of Mycobacterium tuberculosis

Microbiology ◽  
2009 ◽  
Vol 155 (4) ◽  
pp. 1332-1339 ◽  
Author(s):  
Sven Malm ◽  
Yvonne Tiffert ◽  
Julia Micklinghoff ◽  
Sonja Schultze ◽  
Insa Joost ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Nitrate Reductase ◽  
Nitrite Reductase ◽  
Response Regulator ◽  
Specific Binding ◽  
Nitrate Assimilation ◽  
Cosmid Library ◽  
Nitrate Respiration ◽  
Mobility Shift ◽  
Nitrate And Nitrite

Mycobacterium tuberculosis can utilize various nutrients including nitrate as a source of nitrogen. Assimilation of nitrate requires the reduction of nitrate via nitrite to ammonium, which is then incorporated into metabolic pathways. This study was undertaken to define the molecular mechanism of nitrate assimilation in M. tuberculosis. Homologues to a narGHJI-encoded nitrate reductase and a nirBD-encoded nitrite reductase have been found on the chromosome of M. tuberculosis. Previous studies have implied a role for NarGHJI in nitrate respiration rather than nitrate assimilation. Here, we show that a narG mutant of M. tuberculosis failed to grow on nitrate. A nirB mutant of M. tuberculosis failed to grow on both nitrate and nitrite. Mutant strains of Mycobacterium smegmatis mc2155 that are unable to grow on nitrate were isolated. The mutants were rescued by screening a cosmid library from M. tuberculosis, and a gene with homology to the response regulator gene glnR of Streptomyces coelicolor was identified. A ΔglnR mutant of M. tuberculosis was generated, which also failed to grow on nitrate, but regained its ability to utilize nitrate when nirBD was expressed from a plasmid, suggesting a role of GlnR in regulating nirBD expression. A specific binding site for GlnR within the nirB promoter was identified and confirmed by electrophoretic mobility shift assay using purified recombinant GlnR. Semiquantitative reverse transcription PCR, as well as microarray analysis, demonstrated upregulation of nirBD expression in response to GlnR under nitrogen-limiting conditions. In summary, we conclude that NarGHJI and NirBD of M. tuberculosis mediate the assimilatory reduction of nitrate and nitrite, respectively, and that GlnR acts as a transcriptional activator of nirBD.

scholarly journals Nitrate assimilation pathway in higher plants: critical role in nitrogen signalling and utilization

2020 ◽  
Vol 7 (2) ◽  
pp. 182-192
Author(s):  
Ahmad Ali
Keyword(s):  
Nitrate Reductase ◽  
Higher Plants ◽  
Critical Role ◽  
Nitrate Assimilation ◽  
Glutamate Synthase ◽  
Subcellular Location ◽  
Sustainable Growth ◽  
Carbon Skeleton ◽  
Growth And Yield ◽  
The Cost

The process of nitrate assimilation is a very crucial pathway for the sustainable growth and productivity of higher plants. This process is catalysed by two enzymes, nitrate reductase and nitrite reductase. Both the enzymes differ from each other with respect to their structural organisation, subcellular location, catalytic efficiencies and regulatory mechanisms. Nitrate reductase catalyses the rate limiting step of nitrate assimilation process. The genes and proteins of this enzyme have been isolated and characterised from many higher plants. The additional role of NR in the production of nitric oxide has been also reported in last several years. The reduced ammonium is assimilated into carbon skeleton, ?-ketoglutarate, by the concerted action of glutamine synthetase and glutamate synthase. Glutamine and glutamate are the transportable forms of nitrogen among various tissues and metabolic processes. The rate of nitrate assimilation is regulated by the rate of uptake of nitrate by nitrate transporters, availability of carbon skeleton, accumulation of nitrogenous end products, light and the rate of photosynthesis. The partitioning of metabolites and resources between carbon and nitrogen metabolism is an important factor for the growth and yield of plants. During the last several decades excess use of nitrogen fertiliser has caused environmental pollution. Efforts have been made to increase the nitrogen use efficiency of plants to reduce the cost on fertiliser and nitrate pollution, increase the productivity and protein content of several commonly used crops. This review discusses the process of nitrate assimilation and its interaction with the carbon metabolism.

scholarly journals Some Characteristics of Nitrate Reductase From Higher Plants

1968 ◽  
Vol 43 (6) ◽  
pp. 930-940 ◽  
Author(s):  
L. E. Schrader ◽  
G. L. Ritenour ◽  
G. L. Eilrich ◽  
R. H. Hageman
Keyword(s):  
Nitrate Reductase ◽  
Higher Plants
Sign in / Sign up

Export Citation Format

Share Document