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

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Query: EC:1.7.1.4 (nitrite reductase)
1,847 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Staphylococcus carnosus reduces nitrate to ammonia in two steps. (i) Nitrate was taken up and reduced to nitrite, and nitrite was subsequently excreted. (ii) After depletion of nitrate, the accumulated nitrite was imported and reduced to ammonia, which again accumulated in the medium. The localization, energy gain, and induction of the nitrate and nitrite reductases in S. carnosus were characterized. Nitrate reductase seems to be a membrane-bound enzyme involved in respiratory energy conservation, whereas nitrite reductase seems to be a cytosolic enzyme involved in NADH reoxidation. Syntheses of both enzymes are inhibited by oxygen and induced to greater or lesser degrees by nitrate or nitrite, respectively. In whole cells, nitrite reduction is inhibited by nitrate and also by high concentrations of nitrite (> or = 10 mM). Nitrite did not influence nitrate reduction. Two possible mechanisms for the inhibition of nitrite reduction by nitrate that are not mutually exclusive are discussed. (i) Competition for NADH nitrate reductase is expected to oxidize the bulk of the NADH because of its higher specific activity. (ii) The high rate of nitrate reduction could lead to an internal accumulation of nitrite, possibly the result of a less efficient nitrite reduction or export. So far, we have no evidence for the presence of other dissimilatory or assimilatory nitrate or nitrite reductases in S. carnosus.
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PMID:Physiology and interaction of nitrate and nitrite reduction in Staphylococcus carnosus. 860 76

Cytochrome cd1-nitrite reductase and nitrous oxide reductase of Thiobacillus denitrificans were purified and characterized by biochemical and immunochemical methods. In contrast to the generally soluble nature of the denitrification enzymes, these two enzymes were isolated from the membrane fraction of T. denitrificans and remained active after solubilization with Triton X-100. The properties of the membrane-derived enzymes were similar to those of their soluble counterparts from the same organism. Nitrous oxide reductase activity was inhibited by acetylene. Nitrite reductase and nitrous oxide reductase cross-reacted with antisera raised against the soluble enzymes from Pseudomonas stutzeri. The nirS, norBC, and nosZ genes encoding the cytochrome cd1-nitrite reductase, nitric oxide reductase, and nitrous oxide reductase, respectively, from P. stutzeri hybridized with genomic DNA from T. denitrificans. Cross-reactivity and similar N-terminal amino acid and gene sequences suggest that the primary structures of the Thiobacillus enzymes are homologous to the soluble proteins from P. stutzeri.
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PMID:Characterization of the membranous denitrification enzymes nitrite reductase (cytochrome cd1) and copper-containing nitrous oxide reductase from Thiobacillus denitrificans. 863 23

The genes that encode the hc-type nitric-oxide reductase from Paracoccus denitrificans have been identified. They are part of a cluster of six genes (norCBQDEF) and are found near the gene cluster that encodes the cd1-type nitrite reductase, which was identified earlier [de Boer, A. P. N., Reijnders, W. N. M., Kuenen, J. G., Stouthamer, A. H. & van Spanning, R. J. M. (1994) Isolation, sequencing and mutational analysis of a gene cluster involved in nitrite reduction in Paracoccus denitrificans, Antonie Leeu wenhoek 66, 111-127]. norC and norB encode the cytochrome-c-containing subunit II and cytochrome b-containing subunit I of nitric-oxide reductase (NO reductase), respectively. norQ encodes a protein with an ATP-binding motif and has high similarity to NirQ from Pseudomonas stutzeri and Pseudomonas aeruginosa and CbbQ from Pseudomonas hydrogenothermophila. norE encodes a protein with five putative transmembrane alpha-helices and has similarity to CoxIII, the third subunit of the aa3-type cytochrome-c oxidases. norF encodes a small protein with two putative transmembrane alpha-helices. Mutagenesis of norC, norB, norQ and norD resulted in cells unable to grow anaerobically. Nitrite reductase and NO reductase (with succinate or ascorbate as substrates) and nitrous oxide reductase (with succinate as substrate) activities were not detected in these mutant strains. Nitrite extrusion was detected in the medium, indicating that nitrate reductase was active. The norQ and norD mutant strains retained about 16% and 23% of the wild-type level of NorC, respectively. The norE and norF mutant strains had specific growth rates and NorC contents similar to those of the wild-type strain, but had reduced NOR and NIR activities, indicating that their gene products are involved in regulation of enzyme activity. Mutant strains containing the norCBQDEF region on the broad-host-range vector pEG400 were able to grow anaerobically, although at a lower specific growth rate and with lower NOR activity compared with the wild-type strain.
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PMID:Mutational analysis of the nor gene cluster which encodes nitric-oxide reductase from Paracoccus denitrificans. 902 86

Nitrite reductase catalyzes the reduction of nitrite to nitric oxide, the first step in denitrification to produce a gaseous product. We have cloned the gene nirK, which encodes the copper-type nitrite reductase from a denitrifying variant of Rhodobacter sphaeroides, strain 2.4.3. The deduced open reading frame has significant identity with other copper-type nitrite reductases. Analysis of the promoter region shows that transcription initiates 31 bases upstream of the translation start codon. The transcription initiation site is 43.5 bases downstream of a putative binding site for a transcriptional activator. Maximal expression of a nirK-lacZ construct in 2.4.3 requires both a low level of oxygen and the presence of a nitrogen oxide. nirK-lacZ expression was severely impaired in a nitrite reductase-deficient strain of 2.4.3. This suggests that nirK expression is dependent on nitrite reduction. The inability of microaerobically grown nitrite reductase-deficient cells to induce nirK-lacZ expression above basal levels in medium unamended with nitrate demonstrates that changes in oxygen concentrations are not sufficient to modulate nirK expression.
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PMID:Characterization and regulation of the gene encoding nitrite reductase in Rhodobacter sphaeroides 2.4.3. 902 88

Persistent infection with Pseudomonas aeruginosa increases interleukin-8 (IL-8) levels and causes dense neutrophil infiltrations in the airway of patients with chronic airway diseases. To investigate the role of P. aeruginosa infection in IL-8 production in the airway of these patients, we examined whether cell lysates of P. aeruginosa could cause IL-8 production from human bronchial epithelial cells. Diluted sonicated supernatants of P. aeruginosa (SSPA) with a mucoid or nonmucoid phenotype stimulated human bronchial epithelial (BET-1A) cells to produce IL-8. In this study, we have purified a 59-kDa heat-stable protein with IL-8-inducing activity from the SSPA by sequential ion-exchange chromatography. The N-terminal sequence of this purified protein completely matched a sequence at the N-terminal part of the mature protein of nitrite reductase from P. aeruginosa. In addition, immunoblotting with a polyclonal immunoglobulin G (IgG) against recombinant Pseudomonas nitrite reductase demonstrated a specific binding to the purified protein. Furthermore, the immunoprecipitates of the SSPA with a polyclonal IgG against recombinant nitrite reductase induced a twofold-higher IL-8 production in the BET-1A cell culture than did the immunoprecipitates of the SSPA with a control IgG. These lines of evidence confirmed that Pseudomonas nitrite reductase was responsible for IL-8 production in the BET-1A cells. The purified nitrite reductase induced maximal expression of IL-8 mRNA in the BET-1A cells at 1 to 3 h after stimulation, and the IL-8 mRNA expression declined by 8 h after stimulation. New protein translation was not required for nitrite reductase-mediated IL-8 mRNA expression in the BET-1A cells. Nitrite reductase stimulated the BET-1A cells, as well as human alveolar macrophages, pulmonary fibroblasts, and neutrophils, to produce IL-8. In contrast, nitrite reductase induced significant levels of tumor necrosis factor alpha and IL-1beta protein only in human alveolar macrophages. These data support the notion that nitrite reductase from P. aeruginosa induces the production of inflammatory cytokines by respiratory cells and may contribute to the pathogenesis of chronic airway diseases and persistent P. aeruginosa infection.
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PMID:Nitrite reductase from Pseudomonas aeruginosa induces inflammatory cytokines in cultured respiratory cells. 919 32

Nitrate is a significant nitrogen source for plants and microorganisms. Recent molecular genetic analyses of representative bacterial species have revealed structural and regulatory genes responsible for the nitrate-assimilation phenotype. Together with results from physiological and biochemical studies, this information has unveiled fundamental aspects of bacterial nitrate assimilation and provides the foundation for further investigations. Well-studied genera are: the cyanobacteria, including the unicellular Synechococcus and the filamentous Anabaena; the gamma-proteobacteria Klebsiella and Azotobacter; and a Gram-positive bacterium, Bacillus. Nitrate uptake in most of these groups seems to involve a periplasmic binding protein-dependent system that presumably is energized by ATP hydrolysis (ATP-binding cassette transporters). However, Bacillus may, like fungi and plants, utilize electrogenic uptake through a representative of the major facilitator superfamily of transport proteins. Nitrate reductase contains both molybdenum cofactor and an iron-sulfur cluster. Electron donors for the enzymes from cyanobacteria and Azotobacter are ferredoxin and flavodoxin, respectively, whereas the Klebsiella and Bacillus enzymes apparently accept electrons from a specific NAD(P)H-reducing subunit. These subunits share sequence similarity with the reductase components of bacterial aromatic ring-hydroxylating dehydrogenases such as toluene dioxygenase. Nitrite reductase contains sirohaem and an iron-sulfur cluster. The enzymes from cyanobacteria and plants use ferredoxin as the electron donor, whereas the larger enzymes from other bacteria and fungi contain FAD and NAD(P)H binding sites. Nevertheless, the two forms of nitrite reductase share recognizable sequence and structural similarity. Synthesis of nitrate assimilation enzymes and uptake systems is controlled by nitrogen limitation in all bacteria examined, but the relevant regulatory proteins exhibit considerable structural and mechanistic diversity in different bacterial groups. A second level of control, pathway-specific induction by nitrate and nitrite in Klebsiella, involves transcription antitermination. Several issues await further experimentation, including the mechanism and energetics of nitrate uptake, the pathway(s) for nitrite uptake, the nature of electron flow during nitrate reduction, and the action of transcriptional regulatory circuits. Fundamental knowledge of nitrate assimilation physiology should also enhance the study of nitrate metabolism in soil, water and other natural environments, a challenging topic of considerable interest and importance.
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PMID:Nitrate assimilation by bacteria. 932 45

The structures of oxidized, reduced, nitrite-soaked oxidized and nitrite-soaked reduced nitrite reductase from Alcaligenes faecalis have been determined at 1.8-2.0 A resolution using data collected at -160 degrees C. The active site at cryogenic temperature, as at room temperature, contains a tetrahedral type II copper site liganded by three histidines and a water molecule. The solvent site is empty when crystals are reduced with ascorbate. A fully occupied oxygen-coordinate nitrite occupies the solvent site in crystals soaked in nitrite. Ascorbate-reduced crystals soaked in a glycerol-methanol solution and nitrite at -40 degrees C remain colorless at -160 degrees C but turn amber-brown when warmed, suggesting that NO is released. Nitrite is found at one-half occupancy. Five new solvent sites in the oxidized nitrite bound form exhibit defined but different occupancies in the other three forms. These results support a previously proposed mechanism by which nitrite is bound primarily by a single oxygen atom that is protonable, and after reduction and cleavage of that N-O bond, NO is released leaving the oxygen atom bound to the Cu site as hydroxide or water.
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PMID:Structure of nitrite bound to copper-containing nitrite reductase from Alcaligenes faecalis. Mechanistic implications. 935 5

The influence of pH on the denitrification activity of a continuous culture of Paracoccus denitrificans was studied in relation to the presence of nitrite. After a transition from aerobic to anaerobic conditions at the suboptimal pH of 6.8, P. denitrificans was not able to build up a functional denitrification pathway. Nitrite accumulated in the medium as the predominant denitrification product. Although the nitrite reductase gene was induced properly, the enzyme could not be detected at sufficient amounts in the culture. These observations was somehow inhibited, or once synthesized nitrite reductase was inactivated, possibly by the high concentrations of nitrous acid (HNO2). Interestingly, when a P. denitrificans culture which was grown to steady-state under anaerobic conditions was then exposed to suboptimal pHs, cells exhibited a reduced overall denitrification activity, but neither nitrite nor any other denitrification intermediate accumulated.
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PMID:Inhibition of denitrification activity but not of mRNA induction in Paracoccus denitrificans by nitrite at a suboptimal pH. 940 3

In aerobically grown Azorhizobium caulinodans strain IRBG 46, in vivo expression of nitrate reductase (NR) and nitrite reductase (NiR) requires the presence of either nitrate or nitrite. On the contrary mere microaerobic conditions are sufficient for the expression of NR and NiR, however, addition of nitrate to the growth medium enhanced the activities of the enzymes. Optimum concentration of nitrate for maximum expression of NR and NiR activities was different in aerobic and microaerobic conditions. Nitrite was released into the medium both in aerobic and microaerobic conditions beyond a particular concentration of nitrate in the medium. Dissimilatory nitrate reduction was affected to a lesser extent by ammonium compared to assimilatory nitrate reduction.
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PMID:Effect of combined nitrogen on the expression of nitrate reductase and nitrite reductase in Azorhizobium caulinodans. 947 63

We report the development of a high-yield heterologous expression system for the copper-containing nitrite reductase from a denitrifying variant of Rhodobacter sphaeroides. Typical yields of wild-type protein are 20 mg L-1, which can be fully loaded with copper. Nitrite reductase contains an unusual blue-green Type 1 copper center with a redox/electron transfer function and a nearby Type 2 center where nitrite binds and is reduced to nitric oxide. The wild-type enzyme was characterized by: (1) its blue-green Type 1 optical spectrum; (2) its EPR spectrum showing rhombic character to its Type 1 center and nitrite perturbation to its Type 2 center; (3) its 247-mV Type 1 midpoint potential which is low relative to other Type 1 centers; and (4) its kinetics as measured by both steady-state and stopped-flow methods. The Type 2 copper reduction potential as monitored by EPR in the absence of nitrite was below 200 mV so that reduction of the Type 2 center by the Type 1 center in the absence of nitrite is not energetically favored. The mutation M182T in which the methionine ligand of Type 1 copper was changed to a threonine resulted in a blue rather than blue-green Type 1 center, a midpoint potential that increased by more than 100 mV above that of the wild-type Type 1 center, and a somewhat reduced nitrite reductase activity. The blue color and midpoint potential of M182T are reminiscent of plastocyanin, but the Type 1 cupric HOMO ground-state electronic g value and copper hyperfine properties of M182T (as well as cysteine and histidine ENDOR hyperfine properties; see next paper) were unchanged from those of the blue-green native Type 1 center. His287 is a residue in the Type 2 region whose imidazole ring was thought to hydrogen bond to the Type 2 axial ligand but not directly to Type 2 copper. The mutation H287E resulted in a 100-fold loss of enzyme activity and a Type 2 EPR spectrum (as well as ENDOR spectra; see next paper) which were no longer sensitive to the presence of nitrite.
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PMID:Spectroscopic, kinetic, and electrochemical characterization of heterologously expressed wild-type and mutant forms of copper-containing nitrite reductase from Rhodobacter sphaeroides 2.4.3. 955 47


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