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

---

Query: EC:1.7.1.2 (nitrate reductase)
3,861 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The total photosynthetic electron flux through PSII [J(e) (PSII)], the electron flux used for carbon assimilation [J(e) (PCR)], the electron flux used for photorespiration [J(e) (PCO)], the electron flux used for Mehler reaction [J(a) (O(2)-depend)] and the electron flux used for nitrogen metabolism [J(a) (O(2)-independ)] in leaves of Rumex K-1, a fodder crop with high protein content, were measured under three levels of nitrogen application (Fig.2). The nitrate reductase (NR) activity, glutamine synthetase (GS) activity, the leaf protein content, the chlorophyll content, P(n) and Phi (PSII) and F(v)/F(m) (Table 1) were also measured. The results showed that with the increase of nitrogen application, the NR and GS activities increased remarkably (Fig.3) and more electron flux was allocated to nitrogen metabolism as well as photorespiration (Fig.2). Nitrogen metabolism and carbon metabolism competed for energy, and the proportion of energy used in nitrogen metabolism to that used in carbon metabolism changed with nitrogen application rate. The electron flux used for nitrogen metabolism is about 15%-21% of the total electron flux under the three levels of nitrogen application (NO(3)(-) 0-30 mmol/L). Under lower nitrogen application, though energy used for carbon and nitrogen assimilation remarkably decreased, no significant increase of electron flux allocated to Mehler reaction was observed. The excess excitation energy in the leaves under the lower nitrogen application was efficiently dissipated via other energy dissipation mechanisms to protect the leaves against photo-damage.
...
PMID:[Effects of different nitrogen application rate on allocation of photosynthetic electron flux in Rumex K-1 leaves]. 1796 45

Aspartate kinase (AK, EC 2.7.2.4), homoserine dehydrogenase (HSDH, EC 1.1.1.3) and dihydrodipicolinate synthase (DHDPS, EC 4.2.1.52) were isolated and partially purified from immature Chenopodium quinoa Willd seeds. Enzyme activities were studied in the presence of the aspartate-derived amino acids lysine, threonine and methionine and also the lysine analogue S-2-aminoethyl-l-cysteine (AEC), at 1 mM and 5 mM. The results confirmed the existence of, at least, two AK isoenzymes, one inhibited by lysine and the other inhibited by threonine, the latter being predominant in quinoa seeds. HSDH activity was also shown to be partially inhibited by threonine, whereas some of the activity was resistant to the inhibitory effect, indicating the presence of two isoenzymes, one resistant and another sensitive to threonine inhibition. Only one DHDPS isoenzyme highly sensitive to lysine inhibition was detected. The results suggest that the high concentration of lysine observed in quinoa seeds is possibly due to a combined effect of increased lysine synthesis and accumulation in the soluble form and/or as protein lysine. Nitrogen assimilation was also investigated and based on nitrate content, nitrate reductase activity, amino acid distribution and ureide content, the leaves were identified as the predominant site of nitrate reduction in this plant species. The amino acid profile analysis in leaves and roots also indicated an important role of soluble glutamine as a nitrogen transporting compound.
...
PMID:Lysine biosynthesis and nitrogen metabolism in quinoa (Chenopodium quinoa): study of enzymes and nitrogen-containing compounds. 1800 25

Key groups of nitrogen transforming bacteria and enzyme activities in sediments developed in response to dissolved oxygen (DO) concentration were investigated at four different oxygen supply levels, namely, oxygen saturation condition (DO = 8.60 mg L(-1)), aerobic condition (DO = 6.00 mg L(-1)), anoxic condition (DO = 2.00 mg L(-1)), and anaerobic condition (DO = 0.70 mg L(-1)). The results showed that aerobic heterotrophic bacteria, ammonifying bacteria and nitrifying bacteria in the sediments were positively correlated with DO concentration (r = 0.815-0.897, P < 0.01). Among the four oxygen supply levels, the population of denitrifying bacteria was highest in the sediment under anoxic condition during the whole experiment. The enhanced oxygen supply inhibited the activities of urease, nitrate reductase and nitrite reductase in the sediments. However, A positive correlation (r = 0.841, P < 0.01) between the activity of protease and DO concentration was found in the sediments. The increase in oxygen supply for the overlying water might give a positive effect on nitrification and coupled nitrification-denitrification. Nitrogen released from the sediment was low in the aerobic and oxygen saturation condition.
...
PMID:Effect of dissolved oxygen on nitrogen purification of microbial ecosystem in sediments. 1918 7

Nitrogen (N) remobilization in wheat (Triticum aestivum) plants is crucial because it determines the grain protein concentration and the baking quality of flour. In order to evaluate the influence of cytokinins on N remobilization during N starvation, we analyzed various N remobilization parameters in wheat plants that were watered with 6-benzylaminopurine (BAP) either with or without KNO(3). Besides, the effects of BAP on protein synthesis were evaluated, and the size and ultrastructure of chloroplasts of BAP-treated plants were studied. BAP supply inhibited N remobilization of plants independently of N supply as shown by the increase in protein, Rubisco, chlorophyll, sugar and starch concentrations in the older leaves, the decrease in amino acid and sugar export to the phloem, and the decrease in protein, Rubisco and chlorophyll concentrations in the younger leaves. Besides, BAP supply increased nitrate reductase activity and decreased nitrate concentration, thus suggesting an increased assimilatory capacity. The increase in protein concentration could be explained mainly by a significant decrease in protein degradation and, to a lesser extent, by an increase in protein synthesis. Finally, an increase both in the size of the chloroplast and in the plastoglobuli and starch contents in BAP-supplied plants was observed. We propose that cytokinins retain the sink activity of the older leaves by inhibiting amino acid and sugar export to the phloem and stimulating assimilate accumulation in the chloroplasts of the older leaves. Besides, BAP may increase protein concentration of the older leaves both by decreasing protein degradation and maintaining protein synthesis even under stress conditions.
...
PMID:Cytokinin-induced changes of nitrogen remobilization and chloroplast ultrastructure in wheat (Triticum aestivum). 1954 Jun 18

Assimilatory nitrate reduction (ANR) is a pathway wherein NO(3)(-) is reduced to NH(4)(+), an N species that can be incorporated into the biomass. There is little information about the ANR genes in Archaea and most of the known information has been obtained from cultivable species. In this study, the diversity of the haloarchaeal assimilatory nitrate-reducing community was studied in an extreme saline alkaline soil of the former lake Texcoco (Mexico). Genes coding for the assimilatory nitrate reductase (narB) and the assimilatory nitrite reductase (nirA) were used as functional markers. Primers to amplify and detect partial narB and nirA were designed. The analysis of these amplicons by cloning and sequencing showed that the deduced protein fragments shared >45% identity with other NarB and NirA proteins from Euryarchaeota and <38% identity with other nitrate reductases from Bacteria and Crenarchaeota. Furthermore, these clone sequences were clustered within the class Halobacteria with strong support values in both constructed dendrograms, confirming that desired PCR products were obtained. The metabolic capacity to assimilate nitrate by these haloarchaea seems to be important given that at pH 10 and higher, NH(4)(+) is mostly converted to toxic and volatile NH(3), and NO(3)(-) becomes the preferable N source.
...
PMID:Haloarchaeal assimilatory nitrate-reducing communities from a saline alkaline soil. 1965 27

Nitrogen (N) and nitrate (NO(3)(-)) per se regulate many aspects of plant metabolism, growth, and development. N/NO(3)(-) also suppresses parts of secondary metabolism, including anthocyanin synthesis. Molecular components for this repression are unknown. We report that three N/NO(3)(-)-induced members of the LATERAL ORGAN BOUNDARY DOMAIN (LBD) gene family of transcription factors (LBD37, LBD38, and LBD39) act as negative regulators of anthocyanin biosynthesis in Arabidopsis thaliana. Overexpression of each of the three genes in the absence of N/NO(3)(-) strongly suppresses the key regulators of anthocyanin synthesis PAP1 and PAP2, genes in the anthocyanin-specific part of flavonoid synthesis, as well as cyanidin- but not quercetin- or kaempferol-glycoside production. Conversely, lbd37, lbd38, or lbd39 mutants accumulate anthocyanins when grown in N/NO(3)(-)-sufficient conditions and show constitutive expression of anthocyanin biosynthetic genes. The LBD genes also repress many other known N-responsive genes, including key genes required for NO(3)(-) uptake and assimilation, resulting in altered NO(3)(-) content, nitrate reductase activity/activation, protein, amino acid, and starch levels, and N-related growth phenotypes. The results identify LBD37 and its two close homologs as novel repressors of anthocyanin biosynthesis and N availability signals in general. They also show that, besides being developmental regulators, LBD genes fulfill roles in metabolic regulation.
...
PMID:Members of the LBD family of transcription factors repress anthocyanin synthesis and affect additional nitrogen responses in Arabidopsis. 1993 3

Strain HNR, isolated from a Membrane Bioreactor (MBR), demonstrates a surprising ability to convert ammonium to nitrogen gas under aerobic conditions while growing heterotrophically. On the basis of phylogenetic analysis of the 16S rRNA gene sequence, strain HNR was related to Acinetobacter calcoaceticus (98.9% identity). Nitrogen balance during heterotrophic growth with 120mg/l of NH(4)(+)-N showed that 40.2% of NH(4)(+)-N was in the form of N(2) and 52.1% was found in biomass. Only a trace production was either nitrite or nitrate. Further tests demonstrated that nitrite and nitrate were not reduced by strain HNR under aerobic conditions. Neither nitrate reductase (NR) nor nitrite reductase (NiR) activity was detectable in the aerobic reaction mixtures. However, a 0.051 U activity of hydroxylamine oxidase (HAO) was observed. The nitrogen removal was speculated to be via a hydroxylamine intermediate instead of nitrite, which was different from the conventional nitrogen removal pathway.
...
PMID:Heterotrophic nitrogen removal by a newly isolated Acinetobacter calcoaceticus HNR. 2020 30

Seasonal changes in nitrogen assimilation have been studied in the western English Channel by sampling at approximately weekly intervals for 12 months. Nitrate concentrations showed strong seasonal variations. Available nitrogen in the winter was dominated by nitrate but this was close to limit of detection from May to September, after the spring phytoplankton bloom. The (15)N uptake experiments showed that nitrate was the nitrogen source for the spring phytoplankton bloom but regenerated nitrogen supported phytoplankton productivity throughout the summer. The average annual f-ratio was 0.35, which demonstrated the importance of ammonia regeneration in this dynamic temperate region. Nitrogen uptake rate measurements were related to the phytoplankton responsible by assessing the relative abundance of nitrate reductase (NR) genes and the expression of NR among eukaryotic phytoplankton. Strong signals were detected from NR sequences that are not associated with known phylotypes or cultures. NR sequences from the diatom Phaeodactylum tricornutum were highly represented in gene abundance and expression, and were significantly correlated with f-ratio. The results demonstrate that analysis of functional genes provides additional information, and may be able to give better indications of which phytoplankton species are responsible for the observed seasonal changes in f-ratio than microscopic phytoplankton identification.
...
PMID:Linking phytoplankton community composition to seasonal changes in f-ratio. 2154 1

Abstract Young wheat (C3) and maize (C4) plants were exposed to near-ambient concentrations of ozone in open-top chambers in order to investigate the possible effects of ozone on nitrogen metabolism. Nitrogen was supplied to the plants by adding (15)N-labelled tracer substances via the soil substrate. Enzyme activities (NADH nitrate reductase, nitrite reductase, glutamine synthetase and NADH glutamate dehydrogenase) and the incorporation of (15)N were determined. The findings show that nitrogen metabolism was affected by O(3), however, there were distinct differences between the two species. In plants treated with O(3), NADH nitrate reductase activity in maize leaves was reduced, while NR activity in wheat leaves only slightly declined. Only minor changes were observed with respect to the activities of nitrite reductase, glutamine synthetase and NADH glutamate dehydrogenase. Feeding experiments using (15)NO(3) (-) showed that the incorporation of nitrate nitrogen in wheat plants exposed to ozone remains virtually unchanged, whereas in maize plants reduced incorporation rates were observed for nitrate nitrogen. The incorporation of ammonium nitrogen was distinctly increased in wheat and maize by the impact of ozone. When investigating pigment contents, reduced levels of chlorophyll a and b and carotenoids were observed, whereas the pigment content of wheat leaves remained unchanged. These results indicate that young maize plants are more susceptible than wheat plants to short-term ozone exposure.
...
PMID:The impact of ozone on the (15)n incorporation and nitrogen assimilation of wheat and maize. 2208 9

Solar ultraviolet radiation (UVR, 280-400 nm) is known to inhibit the photosynthesis of macroalgae, whereas nitrogen availability may alter the sensitivity of the algae to UVR. Here, we show that UV-B (280-315 nm) significantly reduced the net photosynthetic rate of Gracilaria lemaneiformis. This inhibition was alleviated by enrichment with ammonia, which also caused a decrease in dark respiration. The presence of both UV-A (315-400 nm) and UV-B stimulated the accumulation of UV-absorbing compounds. However, this stimulation was not affected by enrichment with ammonia. The content of phycoerythrin (PE) was increased by the enrichment of ammonia only in the absence of UVR. Ammonia uptake and the activity of nitrate reductase were repressed by UVR. However, exposure to UVR had an insignificant effect on the rate of nitrate uptake. In conclusion, increased PE content associated with ammonia enrichment played a protective role against UVR in this alga, and UVR differentially affected the uptake of nitrate and ammonia.
...
PMID:NH4+ enrichment and UV radiation interact to affect the photosynthesis and nitrogen uptake of Gracilaria lemaneiformis (Rhodophyta). 2210 17


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---