Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.7.1.2 (nitrate reductase)
 3,861 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The first step in the respiratory reduction of nitrate to dinitrogen in Paracoccus pantotrophus is catalyzed by the quinol-nitrate oxidoreductase NarGHI. This membrane-anchored protein directs electrons from quinol oxidation at the membrane anchor, NarI, to the site of nitrate reduction in the membrane extrinsic [Fe-S] cluster and Mo-bis-MGD containing dimer, NarGH. Liberated from the membrane, NarGH retains its nitrate reductase activity and forms films on graphite and gold electrodes within which direct and facile exchange of electrons between the electrode and the enzyme occurs. Protein film voltammetry has been used to define the catalytic behavior of NarGH in the potential domain and a complex pattern of reversible, nitrate concentration dependent modulation of activity has been resolved. At low nitrate concentrations the local maximum observed in the catalytic current-potential profile reveals how NarGH can catalyze nitrate reduction via two pathways having distinct specificity constants, k(obs)(cat)/K(obs)(M). Catalysis is directed to occur via one of the pathways by an electrochemical event within NarGH. On increasing the nitrate concentration, the local maximum in the catalytic current becomes less distinct, and the catalytic waveform adopts an increasingly sigmoidal form. A pattern of voltammetry similar to that observed during nitrate reduction is observed during reduction of the stereochemically distinct substrate chlorate. Centers whose change of oxidation state may define the novel catalytic voltammetry of NarGH have been identified by EPR-monitored potentiometric titrations and mechanisms by which the electrochemistry of Mo-bis-MGD or [Fe-S] clusters can account for the observed behavior are discussed.
Biochemistry 2001 Sep 25
PMID:Catalytic protein film voltammetry from a respiratory nitrate reductase provides evidence for complex electrochemical modulation of enzyme activity. 1156 Apr 77

A Penicillium chrysogenum strain was isolated for its ability to grow in minimal medium containing the herbicide glyphosate as the only nitrogen source. The presence of concentrations up to 25 mM progressively stimulated the fungal growth rate, which was negligible in media lacking reduced nitrogen. However, glyphosate utilization never exceeded 1 mmol g-1 mycelial dry mass, and below a threshold concentration both herbicide uptake and fungal growth were subject to a lag phase, suggesting that the herbicide may enter the cell by either simple passive diffusion or inducible carriers. Amino acids, possible products of glyphosate breakdown, as well as ammonia, were found to replace the herbicide in restoring mycelial growth. Cells were devoid of detectable nitrate reductase activity, thus the isolate seems to be impaired in its ability to convert nitrate to ammonium. In vitro activity of 5-enol-pyruvyl-shikimate-3-phosphate synthase, the target site of glyphosate action, was highly sensitive to the herbicide. Fungal growth rate was considerably lower when the herbicide was also the only phosphorus source, whereas glyphosate utilization was substantially unaffected, suggesting an unusual route for its degradation. Herbicide metabolism was strongly reduced when other sources of organic nitrogen were made available.
Pest Manag Sci 2001 Sep
PMID:Metabolism of the phosphonate herbicide glyphosate by a non-nitrate-utilizing strain of Penicillium chrysogenum. 1156 7

The areA gene of filamentous fungi encodes a positive-acting transcriptional factor required for the expression of genes involved in the utilisation of nitrogen sources other than ammonium and glutamine. In Aspergillus niger we have isolated three UV-induced areA mutants and constructed a well-defined disruption allele of the areA gene. The areA gene was genetically localised on Linkage Group III, 3.6 map units (m.u.) from bioA1 and 4.5 m.u. from lysA7. Analysis of the expression of the nitrate reductase encoding gene and of nitrate reductase activities show that the mutated areA strains behave as loss-of-function mutants and can be classified as areAr type. In addition, growth tests were performed using several nitrogen sources in combination with glucose. The results suggest that, unlike the case in A. nidulans, in A. niger the AreA protein also plays a role in the presence of ammonium. Furthermore, the spectrum of protease activities secreted by A. niger differs from that produced by A. nidulans, as only A. niger is able to degrade elastin.
Mol Genet Genomics 2001 Sep
PMID:Isolation of UV-induced mutations in the areA nitrogen regulatory gene of Aspergillus niger, and construction of a disruption mutant. 1158 76

Multiple sclerosis is a disease characterized by perivascular infiltrates and demyelination of the white matter in the central nervous system. In this study, we compared the serum and cerebrospinal fluid nitric oxide levels before and after methylprednisolone therapy, and during remission period, and investigated the relationship of nitric oxide to the activity of multiple sclerosis. Cerebrospinal fluid and serum nitric oxide levels were measured blind as nitrite plus nitrate, using the nitrate reductase and Griess reaction method in 20 patients with multiple sclerosis before and after corticosteroid therapy, and during remission period, and in 20 control subjects. Mean cerebrospinal fluid and serum nitric oxide levels were highest in the pretreatment group and lowest in the control group. There was no correlation with nitric oxide levels in these two groups. Although corticosteroid therapy did not have any great effect on Expanded Disability Status Scales, it led to a decrease in nitric oxide levels. The possible cause of this might be the inhibition of nitric oxide synthesis by methylprednisolone, or a decrease in multiple sclerosis activity. We conclude that serum or cerebrospinal fluid nitric oxide levels do not reflect the activity in multiple sclerosis.
Clin Chem Lab Med 2001 Sep
PMID:The effect of corticosteroids on serum and cerebrospinal fluid nitric oxide levels in multiple sclerosis. 1160 81

Phycocyanin is a biliprotein which exerts antioxidative and anti-inflammatory effects in various in vivo and in vitro experimental models. In this study phycocyanin effects on tumor necrosis factor-alpha (TNF alpha) and nitrite levels in serum of mice treated with lipopolysaccharide (LPS) was examined. TNF alpha was measured by cytotoxicity on L-929 cells and nitrite by the Griess reaction, after reduction of all nitrates to nitrites by nitrate reductase, 1 h after LPS injection (0.5 mg/kg i.p.) there was a significant increase in TNF alpha levels in mouse serum. Phycocyanin (50-300 mg/kg p.o.), administered 1 h before LPS, reduced dose-dependently the TNF alpha concentration in serum. After 18 h, LPS (30 mg/kg i.p.) also induced a substantial increase in serum nitrite levels, which were reduced dose-dependently by phycocyanin pretreatment (100-300 mg/kg p.o.). The results indicate that phycocyanin exerts inhibitory effects on TNF alpha and NO production which might be ascribed to the antioxidative properties of the biliprotein.
Arzneimittelforschung 2001 Sep
PMID:Effects of phycocyanin extract on tumor necrosis factor-alpha and nitrite levels in serum of mice treated with endotoxin. 1164 5

Nitrate reductase (NR), the rate-limiting and primary control point of the nitrate assimilation pathway, is regulated at transcriptional and post-transcriptional levels. To better understand how NR is regulated at the transcriptional level in Chlorella vulgaris, studies were performed to identify the factors regulating NR expression. Sequence analysis of the NR promoter identified a number of potential sites that were investigated by mobility shift assays. Of the protein-binding sites found, several., such as USF and E2F are likely involved in the basal NR gene transcription. An indirect repeat sequence with similarity to the sequence recognized by the common plant regulatory factor was identified and shown to bind a Chlorella protein in vitro. Mobility shift assays of a consensus GATA element indicated that proteins able to specifically bind this element are constitutive, regardless of the nitrogen source. Mutational analysis revealed that the GATA core is required for protein binding in vitro. Additionally, a NIT2 zinc-finger domain/glutathione S-transferase fusion protein was found to bind in a sequence-specific manner to this site. In Neurospora crassa and Aspergillus nidulans, consensus GATA elements are bound by the NIT2 protein, which has a major role in the expression of nitrogen-metabolizing genes. The ability of the GATA element to function as a nitrogen response element (NRE) was further examined by in vivo foot-printing. The protection of guanines in the GATA core and surrounding region was observed only in cells grown in the presence of nitrate. These data confirm that a single GATA element has a role in regulating the expression of NR in C. vulgaris.
Curr Genet 2001 Sep
PMID:Transcriptional regulation of the nitrate reductase gene in Chlorella vulgaris: identification of regulatory elements controlling expression. 1168 Aug 22

The transcription factor Fnr (fumarate nitrate reductase regulator) globally regulates gene expression in response to oxygen deprivation in Escherichia coli. We report here the cloning and sequencing of the fnr gene from the facultative anaerobic bacterium Klebsiella pneumoniae M5al, another member of the enteric bacteria. The deduced amino acid sequence of K. pneumoniae fnr showed very high similarity (98% amino acid identity) to the Fnr protein from E. coli and contained the four essential cysteine residues which are presumed to build the oxygen-sensing [4Fe4S]+2 center. Transfer of the K. pneumoniae gene to a fnr mutant of E. coli complemented the mutation and permitted synthesis of nitrate reductase and fumarate reductase during anaerobic growth. A gene fusion between K. pneumoniae fnr and glutathione S-transferase was constructed and expressed in E. coli under anaerobic conditions in order to make the protein available in preparative amounts. The overproduced protein was purified by glutathione-Sepharose 4B affinity chromatography in the absence of oxygen, and biochemically characterized.
Antonie Van Leeuwenhoek 2001 Sep
PMID:Cloning, sequencing and characterization of Fnr from Klebsiella pneumoniae. 1181 75

Strawberries (Fragaria xananassa Duch. 'Osogrande') were grown hydroponically with three NO3-N concentrations (3.75, 7.5, or 15.0 mM) to determine effects of varying concentration on NO3-N uptake and reduction rates, and to relate these processes to growth and fruit yield. Plants were grown for 32 weeks, and NO3-N uptake and nitrate reductase (NR) activities in roots and shoots were measured during vegetative and reproductive growth. In general, NO3-N uptake rates increased as NO3-N concentration in the hydroponics system increased. Tissue NO3- concentration also increased as external NO3-N concentration increased, reflecting the differences in uptake rates. There was no effect of external NO3-N concentration on NR activities in leaves or roots during either stage of development. Leaf NR activity averaged approximately 360 nmol NO2 formed/g fresh weight (FW)/h over both developmental stages, while NR activity in roots was much lower, averaging approximately 115 nmol NO2 formed/g FW/h. Vegetative organ FW, dry weight (DW), and total fruit yield were unaffected by NO3-N concentration. These data suggest that the inability of strawberry to increase growth and fruit yield in response to increasing NO3-N concentrations is not due to limitations in NO3-N uptake rates, but rather to limitations in NO3- reduction and/or assimilation in both roots and leaves.
J Am Soc Hortic Sci 2001 Sep
PMID:Nitrate concentration effects on NO3-N uptake and reduction, growth, and fruit yield in strawberry. 1203 27

A field experiment was conducted for two years to study the effect of application of different distillery effluents: raw spent wash (RSW), biomethanated spent wash (BSW), lagoon sludge (LS), recommended NPK + FYM (farm yard manure) and control (no fertilizer and effluent) on some physiological aspects in maize. The study revealed that the application of distillery effluents resulted in increased leaf area, chlorophyll content, nitrate reductase activity total dry weight and grain yield. Among the effluents, the highest grain yield (36.9 qha(-1)) was obtained in BSW followed by RSW (32.2 qha(-1)) and LS (28.3 qha(-1)). Overall, NPK + FYM treatment recorded the highest grain yield (51.8 qha(-1)). However, to achieve the full manurial potential of the effluents, some amount of fertilizer should be supplemented.
Bioresour Technol 2002 Sep
PMID:Effect of distillery effluents on some physiological aspects in maize. 1211 10

Paracoccus pantotrophus can express a periplasmic nitrate reductase (Nap) during aerobic growth. A proposed role for this enzyme is the dissipation of excess redox energy during oxidative metabolism of reduced carbon substrates. To investigate the regulation of nap expression, a transcriptional fusion between the nap promoter region of P. pantotrophus and the lacZ gene was constructed. When this fusion was used, analyses showed that transcription from the nap promoter increases as the average reduction state of the carbon atoms increases. Thus, beta-galactosidase activities increase as the carbon source changes in the order succinate-acetate-butyrate. This result was obtained regardless of which of the three carbon sources was used for culture of the inoculum. If two carbon sources were presented together, the beta-galactosidase activity was always the same as it was when the least-reduced carbon source was added alone. This suggests that the regulation is dependent upon metabolism of the more-reduced carbon sources rather than just their presence in the medium. Analysis of culture medium by (1)H nuclear magnetic resonance showed that for aerobic growth P. pantotrophus strictly selected its carbon source in the order succinate-acetate-butyrate. This was reflected by diauxic growth kinetics on medium containing mixed carbon substrates. The regulatory mechanism underpinning such a selection is unknown but is likely to be related to the mechanism which controls the transcription of the nap operon.
J Bacteriol 2002 Sep
PMID:Hierarchy of carbon source selection in Paracoccus pantotrophus: strict correlation between reduction state of the carbon substrate and aerobic expression of the nap operon. 1216 1


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