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

Pseudomonas aeruginosa can reduce nitrate to nitrite and evenutally to nitrogen gas by the denitrification pathway, thereby providing the organism with a mode of respiration and ATP generation in the absence of oxygen. P. aeruginosa can also reduce nitrate to nitrite through an assimilatory pathway that provides the cell with reduced nitrogen for biosyntheses. In order to establish whether this organism synthesizes a single nitrate reductase protein that functions in both pathways, or produces one for each pathway, we isolated mutants blocked in the assimilation of nitrate. These mutants are unaffected in the reduction of nitrate be the denitrification pathway, although they produce low or undectable levels of assimilatory nitrate reductase. On the basis of transductional analysis, the mutations were found to be distributed among four genes designated nasA, nasB, nasC, and nasD. Shifting a nasA mutant from anaerobic to aerobic growth eliminated the culture's ability to reduce nitrate, i.e. the anaerobic nitrate reductase cannot function in the presence of oxygen. Thus P. aeruginosa can synthesize two distinct proteins which reduce nitrate to nitrite: an assimilatory nitrate reductase and a dissimilatory nitrate reductase. If conditions of growth are fully aerobic, the latter is not synthesized and does not function. The former, synthesized under the control of at least four genes, is repressed by readily available nitrogen sources.
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PMID:Isolation and analysis of mutants of Pseudomonas aeruginosa unable to assimilate nitrate. 12 Jul 27

1. Starved cells of a glucose-grown strain of Staphylococcus aureus are resistant to the action of staphylococcin 1580. Reinitiation of sensitivity is readily obtained upon the addition of glucose, but only weakly with L-lactate, although the latter induces higher ATP levels and supports L-glutamic acid uptake better than glucose does. The NADH/NAD+ ratio correlates with the staphylococcin sensitivity. 2. Starved pyruvate-grown cells remain partially susceptible and full sensitivity is restored both in the presence of glucose and L-lactate. 3. Arsenate but not dicyclohexylcarbodiimide (DCCD) blocks the reinitiation of sensitivity in the presence of glucose. Both arsenate and DCCD block sensitivity in the presence of L-lactate. 4. Aerobically grown cells are sensitive to staphylococcin 1580 under anaerobic conditions. Anaerobically grown cells are less susceptible, but sensitivity can be restored by glucose and also by L-lactate plus nitrate when cells are previously induced for nitrate reductase. 5. Starved cells of a mutant strain defective in the maintenance of a high-energy state of the membrane are normally sensitive in the presence of glucose, but resistant in the presence of L-lactate. A strain lacking a functional respiratory chain (men-) is also sensitive with glucose but resistant in the presence of L-lactate. 6. It is concluded that the initiation of the staphylococcin 1580 action is under control of a mechanism regulating the energy flow in the cell, and involving the presence of a high-energy phosphorylated compound.
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PMID:Energy requirements for the action of staphylococcin 1580 in Staphyloccus aureus. 20 62

In E. coli K12 (F'nif+Kp) hybrids, electron-transport-dependent phosphorylation is not necessary for anaerobic nitrogen fixation, and substrate level phosphorylation can provide sufficient ATP from glucose for nitrogenase activity. The fumarate-reduction system, however, is essential in these hybrids for the transfer of electrons to nitrogenase. This system is probably also involved in maintaining the membrane in the energized state, thereby allowing nitrogen fixation to occur. The nitrate-reduction system, which can energize the membrane like the fumarate-reduction system, is not necessary for nitrogenase activity in the E. coli K12(F'nif+Kp) hybrids. However, two nitrate reductase genes, chlA, and chlB, are essential for inhibition of nitrogen fixation by nitrate. Moreover, nitrate inhibits nitrogenase activity and this inhibition is most probably effected through a regulator factor coded by chlA and chlB.
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PMID:Pathways of energy metabolism required for phenotypic expression of nif+Kp genes in Escherichia coli. 39 94

When anaerobic cultures of Propionibacterium pentosaceum were shifted to low dissolved-oxygen concentration (D.O.C.), acetate production from lactate diminished and propionate production stopped, whereas pyruvate accumulated and oxygen was consumed. Assuming that energy is generated in the electron transfer to oxygen, YATP values (g dry wt bacteria/mole ATP) of between 7.2 and 11.9 were calculated from molar growth yields and product formation. When oxidative phosphorylation in the electron transfer to oxygen was ignored, unreasonably high YATP values were obtained. From these results it is concluded that energy is indeed generated in the electron transfer to oxygen. However, synthesis of cytochrome b was strongly repressed by oxygen. Furthermore, synthesis of all catabolic enzymes studied was impaired in bacteria growing at low D.O.C. Thus, the anaerobic character of P. pentosaceum may be explained by the inhibition of synthesis of both cytochrome b and enzymes in the presence of oxygen. It was demonstrated that nitrate reductase is synthesized constitutively in P. pentosaceum. Synthesis of nitrate reductase was stimulated by nitrate and repressed by oxygen. Synthesis of fumarate reductase was also repressed by oxygen, whereas only a small effect of nitrate on this enzyme was observed. However, propionate formation is inhibited during growth with nitrate. The absence of propionate formation in the presence of oxygen and nitrate is explained by inavailability of NADH needed for the conversion of oxaloacetate into malate in the reductive pathway to succinate, so that succinate and propionate cannot be formed.
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PMID:Lactate metabolism in Propionibacterium pentosaceum growing with nitrate or oxygen as hydrogen acceptor. 108 38

A 3.7-kb DNA region encoding part of the Rhodospirillum rubrum CO oxidation (coo) system was identified by using oligonucleotide probes. Sequence analysis of the cloned region indicated four complete or partial open reading frames (ORFs) with acceptable codon usage. The complete ORFs, the 573-bp cooF and the 1,920-bp cooS, encode an Fe/S protein and the Ni-containing carbon monoxide dehydrogenase (CODH), respectively. The four 4-cysteine motifs encoded by cooF are typical of a class of proteins associated with other oxidoreductases, including formate dehydrogenase, nitrate reductase, dimethyl sulfoxide reductase, and hydrogenase activities. The R. rubrum CODH is 67% similar to the beta subunit of the Clostridium thermoaceticum CODH and 47% similar to the alpha subunit of the Methanothrix soehngenii CODH; an alignment of these three peptides shows relatively limited overall conservation. Kanamycin cassette insertions into cooF and cooS resulted in R. rubrum strains devoid of CO-dependent H2 production with little (cooF::kan) or no (cooS::kan) methyl viologen-linked CODH activity in vitro, but did not dramatically alter their photoheterotrophic growth on malate in the presence of CO. Upstream of cooF is a 567-bp partial ORF, designated cooH, that we ascribe to the CO-induced hydrogenase, based on sequence similarity with other hydrogenases and the elimination of CO-dependent H2 production upon introduction of a cassette into this region. From mutant characterizations, we posit that cooH and cooFS are not cotranscribed. The second partial ORF starts 67 bp downstream of cooS and would be capable of encoding 35 amino acids with an ATP-binding site motif.
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PMID:Genetic and physiological characterization of the Rhodospirillum rubrum carbon monoxide dehydrogenase system. 164 55

The nitrogenase activity, nitrate reductase activity and oxygen uptake as well as the hydrogen incorporation and ATP content were examined in the root nodules and bacteroids, respectively, formed by Rhizobium leguminosarum strains 128C53 (hydrogenase positive) and 300 (hydrogenase negative) in symbiosis with Pisum sativum plants grown in the presence of 2 mM KNO3. The strain 128C53 showed the greatest values for all parameters analyzed, except for the nitrate reductase activity, which was higher for the strain 300. Similarly, nodule nitrate reductase activity in strain 300 was greater than that in strain 128C53 when plants grew in the absence of combined nitrogen. In general, the highest values were obtained when determinations were made after 7 hours of plant illumination. However, the hydrogenase activity of strain 128C53 and the nitrate reductase activities of both strains increased with the light period, reaching a maximum after 14 hours of illumination. These results suggest that the benefits derived from the superior symbiotic properties and from the presence of hydrogenase activity in strain 128C53 could be counteracted by the higher rates of the nodule nitrate reductase activity in strain 300.
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PMID:[Nitrogenase, hydrogenase and nitrate reductase activities, oxygen consumption, and ATP content in nodules formed by strains of Rhizobium leguminosarum 128C53 and 300 in symbiosis with pea plants]. 307 42

The soluble subcellular fraction of a chlB mutant contains an inactive precursor form of the molybdoenzyme nitrate reductase, which can be activated by the addition to the soluble fraction of protein FA, which is thought to be the active product of the chlB locus. Dialysis or desalting of the chlB soluble fraction leads to the loss of nitrate reductase activation, indicating that some low-molecular-weight material is required for the activation. The protein FA-dependent activation of nitrate reductase can be restored to the desalted chlB soluble fraction by the addition of a clarified extract obtained after heating the chlB soluble fraction at 100 degrees C for 8 min. The heat-stable substance present in this preparation has a molecular weight of approximately 1,000. This substance is distinct from the active molybdenum cofactor since its activity is unimpaired in heat-treated extracts prepared from the organism grown in the presence of tungstate, which leads to loss of cofactor activity. Mutations at the chlA or chlE locus, which are required for molybdenum cofactor biosynthesis, similarly do not affect the activity of the heat-treated extract in the in vitro activation process. Moreover, the active material can be separated from the molybdenum cofactor activity by gel filtration. None of the other known pleiotropic chlorate resistance loci (chlD, chlG) are required for the expression of its activity. Magnesium ATP appears to have a role in the formation of the active substance. We conclude that a low-molecular-weight substance, distinct from the active molybdenum cofactor, is required to bestow activity on the molybdoenzyme nitrate reductase during its biosynthesis.
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PMID:Involvement of a low-molecular-weight substance in in vitro activation of the molybdoenzyme respiratory nitrate reductase from a chlB mutant of Escherichia coli. 330 48

The membrane fraction of Bacterionema matruchotii contains an electron transport chain with oxidizing activity for NADH and succinate. Respiration was inhibited by KCN, 2-heptyl-4-hydroxyquinoline-N-oxide, UV light irradiation and CO. UV light irradiation, analysis of membrane extracts, and reconstitution of respiration in UV light treated membranes suggested that respiration is mediated by a menaquinone derivative. The membranes contained cytochromes a, b, and c. Inhibition studies and the effect of KCN and CO on the cytochrome spectrum indicated the presence of an a+a3 cytochrome oxidase and cytochrome o. The membrane fraction from cells grown under O2-limiting conditions contained nitrate reductase activity. In B. matruchotii, electron transport is coupled to oxidative phosphorylation as judged by the effects of substrates and inhibitors on the intracellular ATP concentration.
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PMID:The electron transport chain of Bacterionema matruchotii. 627 95

The phs chromosomal locus of Salmonella typhimurium is essential for the dissimilatory anaerobic reduction of thiosulfate to hydrogen sulfide. Sequence analysis of the phs region revealed a functional operon with three open reading frames, designated phsA, phsB, and phsC, which encode peptides of 82.7, 21.3, and 28.5 kDa, respectively. The predicted products of phsA and phsB exhibited significant homology with the catalytic and electron transfer subunits of several other anaerobic molybdoprotein oxidoreductases, including Escherichia coli dimethyl sulfoxide reductase, nitrate reductase, and formate dehydrogenase. Simultaneous comparison of PhsA to seven homologous molybdoproteins revealed numerous similarities among all eight throughout the entire frame, hence, significant amino acid conservation among molybdoprotein oxidoreductases. Comparison of PhsB to six other homologous sequences revealed four highly conserved iron-sulfur clusters. The predicted phsC product was highly hydrophobic and similar in size to the hydrophobic subunits of the molybdoprotein oxidoreductases containing subunits homologous to phsA and phsB. Thus, phsABC appears to encode thiosulfate reductase. Single-copy phs-lac translational fusions required both anaerobiosis and thiosulfate for full expression, whereas multicopy phs-lac translational fusions responded to either thiosulfate or anaerobiosis, suggesting that oxygen and thiosulfate control of phs involves negative regulation. A possible role for thiosulfate reduction in anaerobic respiration was examined. Thiosulfate did not significantly augment the final densities of anaerobic cultures grown on any of the 18 carbon sources tested. on the other hand, washed stationary-phase cells depleted of ATP were shown to synthesize small amounts of ATP on the addition of the formate and thiosulfate, suggesting that the thiosulfate reduction plays a unique role in anaerobic energy conservation by S typhimurium.
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PMID:Sequence analysis of the phs operon in Salmonella typhimurium and the contribution of thiosulfate reduction to anaerobic energy metabolism. 775 Dec 91

A pH dependent reduction in growth, pigment, ATP content, O2- evolution, carbon fixation, photosynthetic electron transport system, nutrient uptake (NO3- and NH4+), nitrate reductase, and ATPase activities and increase in K+ efflux of Chlorella vulgaris was noticed following supplementation of Cu and Ni to the culture medium. PS II was found to be more sensitive to both pH and metals than PS I. Though, nitrate reductase (NR) was more sensitive to both pH and metals, the ATPase was however, more sensitive to metals but less sensitive to acidic pH. Acid pH was found to inhibit the nutrient (NO3- and NH4+) uptake and nitrate reductase in a non-competitive manner. The inhibition produced by the test metals alone was of non-competitive type for NO3- uptake, nitrate reductase and ATPase and competitive for NH4+ uptake. Acidity not only inhibited the metabolic variables directly but also through facilitated uptake of metals and increased membrane permeability. A very low sensitivity of ATPase to acidic pH seems to be responsible for the survival of algae in acid environment.
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PMID:Effect of Cu and Ni on growth, mineral uptake, photosynthesis and enzyme activities of Chlorella vulgaris at different pH values. 802 20


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