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Query: UNIPROT:Q8NEX9 (reductase)
 26,410 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The inhibitory effects of nitrate (NO3-) and nitrite (NO2-) on dissimilatory iron (FE3+) reduction were examined in a series of electron acceptor competition experiments using Shewanella putrefaciens 200 as a model iron-reducing microorganism. S. putrefaciens 200 was found to express low-rate nitrate reductase, nitrite reductase, and ferrireductase activity after growth under highly aerobic conditions and greatly elevated rates of each reductase activity after growth under microaerobic conditions. The effects of NO3- and NO2- on the Fe3+ reduction activity of both aerobically and microaerobically grown cells appeared to follow a consistent pattern; in the presence of Fe3+ and either NO3- or NO2-, dissimilatory Fe3+ and nitrogen oxide reduction occurred simultaneously. Nitrogen oxide reduction was not affected by the presence of Fe3+, suggesting that S. putrefaciens 200 expressed a set of at least three physiologically distinct terminal reductases that served as electron donors to NO3-, NO2-, and Fe3+. However, Fe3+ reduction was partially inhibited by the presence of either NO3- or NO2-. An in situ ferrozine assay was used to distinguish the biological and chemical components of the observed inhibitory effects. Rate data indicated that neither NO3- nor NO2- acted as a chemical oxidant of bacterially produced Fe2+. In addition, the decrease in Fe3+ reduction activity observed in the presence of both NO3- and NO2- was identical to the decrease observed in the presence of NO2- alone. These results suggest that bacterially produced NO2- is responsible for inhibiting electron transport to Fe3+.
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PMID:Effects of nitrate and nitrite on dissimilatory iron reduction by Shewanella putrefaciens 200. 154 35

Denitrification and methylotrophy in Paracoccus denitrificans are discussed. The properties of the enzymes of denitrification: the nitrate-nitrite antiporter, nitrate reductase, nitrite reductase, nitric oxide reductase and nitrous oxide reductase are described. The genes for none of these proteins have yet been cloned and sequenced from P. denitrificans. A number of sequences are available for enzymes from Escherichia coli, Pseudomonas stutzeri and Pseudomonas aeruginosa. It is concluded that pathway specific c-type cytochromes are involved in denitrification. At least 40 genes are involved in denitrification. In methanol oxidation at least 20 genes are involved. In this case too pathway specific c-type cytochromes are involved. The sequence homology between the quinoproteins methanol dehydrogenase, alcoholde-hydrogenase and glucose dehydrogenase is discussed. This superfamily of proteins is believed to be derived from a common ancestor. The moxFJGI operon determines the structural components of methanol dehydrogenase and the associated c-type cytochrome. Upstream of this operon 3 regulatory proteins were found. The moxY protein shows the general features of a sensor protein and the moxX protein those of a regulatory protein. Thus a two component regulatory system is involved in both denitrification and methylotrophy. The phylogeny of prokaryotes based on 16S rRNA sequence is discussed. It is remarkable that the 16S rRNA of Thiosphaera pantotropha is identical to that of P. denitrificans. Still these bacteria show a number of differences. T. pantotropha is able to denitrify under aerobic circumstances and it shows heterotrophic nitrification. Nitrification and heterotrophic nitrification are found in species belonging to the beta-and gamma-subdivisions of purple non-sulfur bacteria. Thus the occurrence of heterotrophic nitrification in T. pantotropha, which belongs to the alpha-subdivision of purple non-sulfur bacteria is a remarkable property. Furthermore T. pantotropha contains two nitrate reductases of which the periplasmic one is supposed to be involved in aerobic denitrification. The nitrite reductase is of the Cu-type and not of the cytochrome cd1 type as in P. denitrificans. Also the cytochrome b of the Qbc complex of T. pantotropha is highly similar to its counterpart in P. denitrificans. It is hypothesized that the differences between these two organisms which both contain large megaplasmids is due to a combination of loss of genetic information and plasmid-coded properties. The distribution of a number of complex metabolic systems in eubacteria and in a number of species belonging to the alpha-group of purple non sulphur bacteria is reviewed.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Metabolic pathways in Paracoccus denitrificans and closely related bacteria in relation to the phylogeny of prokaryotes. 157 65

The enzymes catalyzing the initial reactions in the anaerobic degradation of 2-aminobenzoic acid (anthranilic acid) were studied with a denitrifying Pseudomonas sp. anaerobically grown with 2-aminobenzoate and nitrate as the sole carbon and energy sources. Cells grown on 2-aminobenzoate are simultaneously adapted to growth with benzoate, whereas cells grown on benzoate degrade 2-aminobenzoate several times less efficiently than benzoate. Evidence for a new reductive pathway of aromatic metabolism and for four enzymes catalyzing the initial steps is presented. The organism contains 2-aminobenzoate-coenzyme A ligase (2-aminobenzoate-CoA ligase), which forms 2-aminobenzoyl-CoA. 2-Aminobenzoyl-CoA is then reductively deaminated to benzoyl-CoA by an oxygen-sensitive enzyme, 2-aminobenzoyl-CoA reductase (deaminating), which requires a low potential reductant [Ti(III)]. The specific activity is 15 nmol of 2-aminobenzoyl-CoA reduced min-1 mg-1 of protein at an optimal pH of 7. The two enzymes are induced by the substrate under anaerobic conditions only. Benzoyl-CoA is further converted in vitro by reduction with Ti(III) to six products; the same products are formed when benzoyl-CoA or 2-aminobenzoyl-CoA is incubated under reducing conditions. Two of them were identified preliminarily. One product is cyclohex-1-enecarboxyl-CoA, the other is trans-2-hydroxycyclohexane-carboxyl-CoA. The complex transformation of benzoyl-CoA is ascribed to at least two enzymes, benzoyl-CoA reductase (aromatic ring reducing) and cyclohex-1-enecarboxyl-CoA hydratase. The reduction of benzoyl-CoA to alicyclic compounds is catalyzed by extracts from cells grown anaerobically on either 2-aminobenzoate or benzoate at almost the same rate (10 to 15 nmol min-1 mg-1 of protein). In contrast, extracts from cells grown anaerobically on acetate or grown aerobically on benzoate or 2-aminobenzoate are inactive. This suggests a sequential induction of the enzymes.
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PMID:Anaerobic degradation of 2-aminobenzoic acid (anthranilic acid) via benzoyl-coenzyme A (CoA) and cyclohex-1-enecarboxyl-CoA in a denitrifying bacterium. 159 16

Bacterial denitrification reverses nitrogen fixation in the global N-cycle by transforming nitrate or nitrite to dinitrogen. Both nitrite and nitric oxide (NO) are considered as the chemical species within the denitrification pathway, that precede nitrous oxide (N2O), the first recognized intermediate with N,N-bonds antecedent to N2. Molecular cloning of the structural genes for NO reductase from Pseudomonas stutzeri has allowed us to generate the first mutants defective in NO utilization (Nor- phenotype) by marker exchange of the norCB genes with a gene cassette for gentamicin resistance. Nitric oxide reductase was found to be an indispensable component for denitrification; its loss constituted a conditionally lethal mutation. NO as the sole product accumulated from nitrite by mutant cells induced for nitrite respiration (denitrification). The Nor- mutant lost the capability to reduce NO and did not grow anymore anaerobically on nitrate. A Nir-Nor- double mutation, that inactivated also the respiratory nitrite reductase cytochrome cd1 rendered the bacterium again viable under anaerobiosis. Our observations provide evidence for a denitrification pathway in vivo of NO2(-)----NO----N2O, and N,N-bond formation catalyzed by NO reductase and not by cytochrome cd1.
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PMID:Marker exchange of the structural genes for nitric oxide reductase blocks the denitrification pathway of Pseudomonas stutzeri at nitric oxide. 174 72

Nucleotide sequences were determined for cDNA clones for squash NADH:nitrate oxidoreductase (EC 1.6.6.1), which is one of the most completely characterized forms of this higher plant enzyme. An open reading frame of 2754 nucleotides began at the first ATG. The deduced amino acid sequence contains 918 residues, with a predicted Mr = 103,376. The amino acid sequence is very similar to sequences deduced for other higher plant nitrate reductases. The squash sequence has significant similarity to the amino acid sequences of sulfite oxidase, cytochrome b5, and NADH:cytochrome b5 reductase. Alignment of these sequences with that of squash defines domains of nitrate reductase that appear to bind its 3 prosthetic groups (molybdopterin, heme-iron, and FAD). The amino acid sequence of the FAD domain of squash nitrate reductase was aligned with FAD domain sequences of other NADH:nitrate reductases, NADH:cytochrome b5 reductases, NADPH:nitrate reductases, ferredoxin:NADP+ reductases, NADPH:cytochrome P-450 reductases, NADPH:sulfite reductase flavoproteins, and Bacillus megaterium cytochrome P-450BM-3. In this multiple alignment, 14 amino acid residues are invariant, which suggests these proteins are members of a family of flavoenzymes. Secondary structure elements of the structural model of spinach ferredoxin:NADP+ reductase were used to predict the secondary structure of squash nitrate reductase and the other related flavoenzymes in this family. We suggest that this family of flavoenzymes, nearly all of which reduce a hemoprotein, be called "flavoprotein pyridine nucleotide cytochrome reductases."
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PMID:The sequence of squash NADH:nitrate reductase and its relationship to the sequences of other flavoprotein oxidoreductases. A family of flavoprotein pyridine nucleotide cytochrome reductases. 174 31

When a new strain of Pseudomonas aeruginosa was grown aerobically and then transferred to anaerobic conditions, cells reduced NO3- quantitatively to NO2- in NO3(-)-respiration. In the absence of nitrate, NO2- was immediately reduced to NO or N2O but not to N2 indicating that NO2(-)-reductase but not N2O-reductase was active. The formation of the products NO or N2O depended on the pH in the medium and the concentration of NO2- present. When P. aeruginosa was grown anaerobically for at least three days N2O-reductase was also active. Such cells reduced NO to N2 via N2O. The new strain generated at H(+)-gradient and grew by reducing N2O to N2 but not by converting NO to N2O. For comparison, Azospirillum brasilense Sp7 showed the same pattern of NO-reduction. In contrast, Paracoccus denitrificans formed 3.5 H+/NO during the reduction of NO to N2O in oxidant pulse experiments but could not grow in the presence of NO. Thus the NO-reduction pattern in P. denitrificans on one side and P. aeruginosa and A. brasilense on the other was very different. The mechanistic implications of such differences are discussed.
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PMID:The production and utilization of nitric oxide by a new, denitrifying strain of Pseudomonas aeruginosa. 177 47

Use of Clark-type electrodes has shown that, in cells of Thiosphaera pantotropha, the nitrous oxide reductase is active in the presence of O2, and that the two gases involved (N2O, O2) are reduced simultaneously, but with mutual inhibition. Reduction of nitrate, or nitrite, to N2O under aerobic conditions involves NO as an intermediate, as judged by trapping experiments with the ferric form of extracellular horse heart cytochrome c and the demonstration that the cells possess a nitric oxide reductase activity. The overall conversion of nitrate to N2, the process of denitrification, under aerobic conditions, is thus not prevented by reaction of NO with O2 and depends upon a nitrous oxide reductase system which differs from that in other organisms by being neither directly inhibited nor inactivated by O2.
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PMID:Nitric and nitrous oxide reductases are active under aerobic conditions in cells of Thiosphaera pantotropha. 184 42

Nitrite reductase is the second enzyme in the nitrate assimilatory pathway. The transcription of this gene is regulated by nitrate as well as a variety of other environmental and developmental factors. Genomic clones containing the entire nitrite reductase gene have been isolated from a spinach genomic library and sequenced. The sequence is identical in the transcribed region to a previously isolated spinach NiR cDNA clone (Back et al., 1988) except for the presence of three introns. The analysis of the genomic clones and DNA blot hybridization demonstrates that there is a single NiR gene per haploid genome in spinach. This is in contrast to what has been found for other plant species. The transcription initiation site has been determined by S1 mapping and the 5' upstream region has been used to regulate the GUS reporter gene in transgenic tobacco plants. This gene was found to be regulated by the addition of nitrate in the transgenic plants.
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PMID:Isolation of the spinach nitrite reductase gene promoter which confers nitrate inducibility on GUS gene expression in transgenic tobacco. 186 26

Pseudomonas aeruginosa is an obligate respirer which can utilize nitrate as a terminal electron acceptor under anaerobic conditions (denitrification). Immediate, transient regulation of nitrate respiration is mediated by oxygen through the inhibition of nitrate uptake. In order to gain an understanding of the bioenergetics of nitrate transport and its regulation by oxygen, the effects of various metabolic inhibitors on the uptake process and on oxygen regulation were investigated. Nitrate uptake was stimulated by the protonophores carbonyl cyanide m-chlorophenylhydrazone and 2,4-dinitrophenol, indicating that nitrate uptake is not strictly energized by, but may be affected by the proton motive force. Oxygen regulation of nitrate uptake might in part be through redox-sensitive thiol groups since N-ethylmaleimide at high concentrations decreased the rate of nitrate transport. Cells grown with tungstate (deficient in nitrate reductase activity) and azide-treated cells transported nitrate at significantly lower rates than untreated cells, indicating that physiological rates of nitrate transport are dependent on nitrate reduction. Furthermore, tungstate grown cells transported nitrate only in the presence of nitrite, lending support to the nitrate/nitrite antiport model for transport. Oxygen regulation of nitrate transport was relieved (10% that of typical anaerobic rates) by the cytochrome oxygen reductase inhibitors carbon monoxide and cyanide.
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PMID:Nitrate transport and its regulation by O2 in Pseudomonas aeruginosa. 191 Feb 83

Dimethyl sulfoxide (DMSO) reductase of Escherichia coli is a membrane-bound, terminal anaerobic electron transfer enzyme composed of three nonidentical subunits. The DmsAB subunits are hydrophilic and are localized on the cytoplasmic side of the plasma membrane. DmsC is the membrane-intrinsic polypeptide, proposed to anchor the extrinsic subunits. We have constructed a number of strains lacking portions of the chromosomal dmsABC operon. These mutant strains failed to grow anaerobically on glycerol minimal medium with DMSO as the sole terminal oxidant but exhibited normal growth with nitrate, fumarate, and trimethylamine N-oxide, indicating that DMSO reductase is solely responsible for growth on DMSO. In vivo complementation of the mutant with plasmids carrying various dms genes, singly or in combination, revealed that the expression of all three subunits is essential to restore anaerobic growth. Expression of the DmsAB subunits without DmsC results in accumulation of the catalytically active dimer in the cytoplasm. The dimer is thermolabile and catalyzes the reduction of various substrates in the presence of artificial electron donors. Dimethylnaphthoquinol (an analog of the physiological electron donor menaquinone) was oxidized only by the holoenzyme. These results suggest that the membrane-intrinsic subunit is necessary for anchoring, stability, and electron transport. The C-terminal region of DmsB appears to interact with the anchor peptide and facilitates the membrane assembly of the catalytic dimer.
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PMID:Dimethyl sulfoxide reductase of Escherichia coli: an investigation of function and assembly by use of in vivo complementation. 191 29


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