Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:Q8NEX9 (reductase)
 26,410 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Structural and chemical properties of a flavodoxin from Anabaena PCC 7119 are described. The first 36 residues of the amino-terminal amino acid sequence have been determined and show extensive homology with flavodoxins isolated from other sources. Anabaena flavodoxin exhibits a net negative change (-3) in the helix-1 segment as found with other cyanobacterial flavodoxins Synechococcus 6301 (Anacystis nidulans) and Nostoc MAC, but in contrast to the net positive charge found in this region in the case of flavodoxins isolated from nitrogen-fixing bacteria (Azotobacter and Klebsiella). The FMN cofactor can be reversibly resolved from the apoprotein by trichloroacetic acid treatment. Apoflavodoxin, thus prepared, binds FMN with a Kd value of 0.1 nM and binds riboflavin with a decreased affinity (Kd = 5 microM) at pH 7.2. The apoprotein is stable in dilute solutions at pH values around 7 but readily denatures at pH 8 as judged from loss in flavin-binding ability and by ultraviolet circular dichroism spectroscopy. Oxidation-reduction potential studies at pH values of 7 and 8 show OX/SQ couples of -195 mV and -255 mV, respectively, and show SQ/HQ couples of -390 mV and -418 mV, respectively. From these data, the binding constant for the FMN semiquinone is calculated to be approx. 5-fold tighter and the binding of the FMN hydroquinone is approx. 10(5)-fold weaker than that of the oxidized FMN to the apoprotein. Anabaena flavodoxin functions as an effective mediator of electron transfer from ferredoxin-NADP(+)-reductase to cytochrome c with a turnover number [4.5-5) x 10(3) min-1); a values similar to that determined for Anabaena ferredoxin. The flavodoxin binds tightly to the reductase with Kd values of 6.4 and 8.5 microM at pH values of 7.0 and 8.0, respectively.
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PMID:Structural and chemical properties of a flavodoxin from Anabaena PCC 7119. 211 31

The flavoenzyme thioredoxin reductase from Escherichia coli contains an oxidation-reduction active disulfide made up of Cys135 and Cys138. Mutations changing each Cys residue to a Ser residue have been effected (Prongay, A. J., engelke, D. R., and Williams, C. H., Jr. (1989) J. Biol. Chem. 264, 2656-2664). The FAD prosthetic group of each altered thioredoxin reductase has been replaced with 1-deaza-FAD (a flavin analog with carbon substituted for nitrogen at position 1), 4-thio-FAD (a flavin analog with sulfur substituted for oxygen at position 4), and 6-thiocyanato-FAD. 1-Deaza-FAD-TRR(Cys135,Ser138) has absorbance and fluorescence spectral properties similar to the oxidized form of wild type apothioredoxin reductase reconstituted with 1-deaza-FAD. The absorbance spectrum of 1-deaza-FAD-TRR(Ser135,Cys138) is similar to the spectrum of the two-electron reduced form of wild type apothioredoxin reductase reconstituted with 1-deaza-FAD, indicating that it is a mixture of two species (O'Donnell, M. E., and Williams, C. H., Jr. (1984) J. Biol. Chem. 259, 2243-2251). The spectrum of one of these species of 1-deaza-FAD-TRR(Ser135,Cys138) resembles the spectrum of oxidized 1-deaza-FAD bound to wild type apothioredoxin reductase. The other species has an absorbance spectrum with a single peak at 400 nm (epsilon 400 = 11,100 M-1 cm-1) and resembles the spectrum of a thiolate adduct at the C4a position of the 1-deaza-FAD. The equilibrium between these species is pH-dependent, with a maximum of 50% C4a-adduct formation at low pH, and is linked to pK alpha values at 8.2 and 9.3. The absorbance spectrum of 4-thio-FAD-TRR(Cys135,Ser138) resembles the spectrum of the unbound 4-thio-FAD, whereas 4-thio-FAD-TRR(Ser135,Cys138) has a spectrum indicative of a mixture of 4-thio-FAD and FAD, suggesting a reaction between the 4-position of the flavin and Cys138. The binding of 6-thiocyanato-FAD to the apoprotein of the mutated enzymes showed no evidence for a reaction between the thiols and the group at the 6-position of the flavin.
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PMID:Evidence for direct interaction between cysteine 138 and the flavin in thioredoxin reductase. A study using flavin analogs. 222 55

The NADPH-linked 3-oxoacyl-(acyl-carrier protein) (ACP) reductase (EC 1.1.1.100), also known as 'beta-ketoacyl-ACP reductase', has been purified from the mesocarp of mature avocado pears (Persea americana). The enzyme is inactivated by low ionic strength and low temperature. On SDS/PAGE under reducing conditions, purified 3-oxoacyl-ACP reductase migrated as a single polypeptide giving a molecular mass of 28 kDa. Gel-filtration chromatography gave an apparent native molecular mass of 130 kDa, suggesting that the enzyme is tetrameric. The enzyme is inactivated by dilution, but some protection is afforded by the presence of NADPH. Kinetic constants have been determined using synthetic analogues as well as the natural ACP substrate. It exhibits a broad pH optimum around neutrality. Phenylglyoxal inactivates the enzyme, and partial protection is given by 1 mM-NADPH. Antibodies have been raised against the protein, which were used to localize it using immunogold electron microscopy. It is localized in plastids. N-Terminal amino-acid-sequence analysis was performed on the enzyme, and it shows close structural similarity with cytochrome f. Internal amino-acid-sequence data, derived from tryptic peptides, shows similarity with the putative gene products encoded by the nodG gene from the nitrogen-fixing bacterium Rhizobium meliloti and the gra III act III genes from Streptomyces spp.
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PMID:3-Oxoacyl-(acyl-carrier protein) reductase from avocado (Persea americana) fruit mesocarp. 224 75

Three sites of inhibitory action of hydroxylamine were identified in the respiratory chain of anaerobically grown bacterium Paracoccus denitrificans. Terminal oxidases were blocked at concentrations of 10(-4) to 10(-3) mol.l-1, and the inhibitor competed with artificial donor of electrons N, N, N', N'-tetramethyl-l, 4-phenylenediamine. In the anaerobic part of the respiratory chain inhibition of nitrite reductase and apparently also nitric oxide reductase occurred, resulting in the increased accumulation of nitric oxide during denitrification. These effects together with the inhibition of terminal oxidases by nitric oxide are probably realized through switching the electron flow from oxygen to nitrogen terminal acceptors in the presence of hydroxylamine. By means of difference spectroscopy, the respiratory inhibitor mucidin and a cytochrome c-deficient mutant of Paracoccus denitrificans, hydroxylamine could be shown to serve also as a terminal acceptor of the cytochrome c region. Reduction of hydroxylamine to ammonia was at the same time accompanied by the formation of transmembrane electrical gradient. Hydroxylamine reductase was purified 123-fold from the periplasmatic cell fraction by FPLC; the product obtained showed the features of respiratory nitrite reductase of the cytochrome cd1 type.
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PMID:Hydroxylamine as an inhibitor and terminal acceptor in the respiratory chain of the bacterium Paracoccus denitrificans. 226 22

Skin from an inbred strain of hairless mouse was used as a homogeneous model tissue for studies of skin cryopreservation. Tetrazolium reductase enzyme activity was used to assess tissue viability. Hepes-buffered 199 tissue culture medium was confirmed to be a suitable basal medium, to which cryoprotectants were added. Addition of serum to the cryoprotective cocktail had no beneficial effect. Three cryoprotectants, dimethyl sulfoxide, ethanediol, and glycerol were evaluated. There was no evidence of specific toxicity attributable to the cryoprotective agents during the permeation period; however, short permeation times at low temperature were associated with maximum skin viability. Following freezing and thawing, higher viabilities were obtained when using a slow (-1 degree C min-1) or medium (-60 degree C min-1) rather than a fast (immersion in liquid nitrogen) cooling rate. Dimethyl sulfoxide was a marginally better cryoprotectant overall, although this difference was not statistically significant.
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PMID:Effects of cryobiological variables on the survival of skin using a defined murine model. 233 89

Nitrogen dioxide (NO2), a major oxidant constituent of vehicle emissions, is toxic to lung cells including endothelial cells. Since NO2 is a reactive free radical, one of the postulated mechanisms of NO2-induced pulmonary injury involves the peroxidation of membrane lipids. Therefore, this study evaluated the dose- and time-dependent effects of nitrogen dioxide exposure by measuring the biochemical and biophysical parameters, as well as the metabolic function, in porcine pulmonary artery and aortic endothelial cells in monolayer cultures. To evaluate the biochemical changes, the antioxidant enzyme GSH-reductase (GSH-red), GSH-peroxidase (GSH-per), and glucose-6-phosphate dehydrogenase (G6PDH) activities, as well as the lipid peroxide formation, glutathione (GSH) content, and lactate dehydrogenase (LDH) release were measured. Biophysical changes were measured by monitoring lipid fluidity in both the hydrophobic and hydrophilic regions of the plasma membrane. The uptake of 5-hydroxytryptamine (5-HT) was measured as a metabolic function of endothelial cells. Confluent porcine pulmonary artery and aortic endothelial cells were exposed to 3 or 5 ppm NO2 or air (control) for 3-24 hours. After 3-, 6-, or 12-hour exposures to 3 or 5 ppm NO2, the GSH-red and G6PDH activities, as well as the lipid peroxide formation and LDH release, were not different from those of controls in both pulmonary artery and aortic endothelial cells. Exposure of the cells to 3 or 5 ppm NO2 for 24 hours resulted in significant increases in GSH-red (p less than 0.05) and G6PDH (p less than 0.001) activities in both cell types. Exposure to 5 ppm NO2 for 24 hours significantly (p less than 0.05) increased lipid peroxide formation and increased (p less than 0.01) LDH release in both the pulmonary artery and aortic endothelial cells. GSH-per activity and GSH content in NO2-exposed pulmonary artery and aortic endothelial cells were not different from those of controls, irrespective of NO2 concentration and exposure time. Fluorescence spectroscopy was used to measure the membrane lipid fluidity. Membrane fluidity in the hydrophobic region was measured by 1,6-diphenyl-1, 3, 5-hexatriene (DPH), an aromatic hydrocarbon that partitions into the hydrophobic interior of the lipid bilayer.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Biochemical and metabolic response to nitrogen dioxide-induced endothelial injury. 247 62

The effect of oxygen, ammonium ion, and amino acids on nitrogenase activity in the root-associated N2-fixing bacterium Herbaspirillum seropedicae was investigated in comparison with Azospirillum spp. and Rhodospirillum rubrum. H. seropedicae is microaerophilic, and its optimal dissolved oxygen level is from 0.04 to 0.2 kPa for dinitrogen fixation but higher when it is supplied with fixed nitrogen. No nitrogenase activity was detected when the dissolved O2 level corresponded to 4.0 kPa. Ammonium, a product of the nitrogenase reaction, reversibly inhibited nitrogenase activity when added to derepressed cell cultures. However, the inhibition of nitrogenase activity was only partial even with concentrations of ammonium chloride as high as 20 mM. Amides such as glutamine and asparagine partially inhibited nitrogenase activity, but glutamate did not. Nitrogenase in crude extracts prepared from ammonium-inhibited cells showed activity as high as in extracts from N2-fixing cells. The pattern of the dinitrogenase and the dinitrogenase reductase revealed by the immunoblotting technique did not change upon ammonium chloride treatment of cells in vivo. No homologous sequences were detected with the draT-draG probe from Azospirillum lipoferum. There is no clear evidence that ADP-ribosylation of the dinitrogenase reductase is involved in the ammonium inhibition of H. seropedicae. The uncoupler carbonyl cyanide m-chlorophenylhydrazone decreased the intracellular ATP concentration and inhibited the nitrogenase activity of whole cells. The ATP pool was not significantly disturbed when cultures were treated with ammonium in vivo. Possible mechanisms for inhibition by ammonium of whole-cell nitrogenase activity in H. seropedicae are discussed.
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PMID:Ammonium inhibition of nitrogenase activity in Herbaspirillum seropedicae. 249 87

Nitrogen fixation activity in the photosynthetic bacterium Rhodospirillum rubrum is controlled by the reversible ADP-ribosylation of the dinitrogenase reductase component of the nitrogenase enzyme complex. This report describes the cloning and characterization of the genes encoding the ADP-ribosyltransferase (draT) and the ADP-ribosylglycohydrolase (draG) involved in this regulation. These genes are shown to be contiguous on the R. rubrum chromosome and highly linked to the nifHDK genes. Sequence analysis revealed the use of TTG as the initiation codon of the draT gene as well as a potential open reading frame immediately downstream of draG. The mono-ADP-ribosylation system in R. rubrum is the first in which both the target protein and modifying enzymes as well as their structural genes have been isolated, making it the model system of choice for analysis of this post-translational regulatory mechanism.
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PMID:Genes coding for the reversible ADP-ribosylation system of dinitrogenase reductase from Rhodospirillum rubrum. 250 27

Among nitrogen oxides, NO and NO2 are free radicals and show a variety of biological effects. NO2 is a strongly oxidizing toxicant, although NO, not oxidizing as NO2, is toxic in that it interacts with hemoglobin to form nitrosyl- and methemoglobin. Nitrosylhemoglobin shows a characteristic electron spin resonance (ESR) signal due to an odd electron localized on the nitrogen atom of NO and reacts with oxygen to yield nitrate and methemoglobin, which is rapidly reduced by methemoglobin reductase in red cells. NO was found to inhibit the reductase activity. Part of NO inhaled in the body is oxidized by oxygen to NO2, which easily dissolves in water and converts to nitrite and nitrate. The nitrite oxidizes oxyhemoglobin autocatalytically after a lag. The mechanism of the oxidation, particularly the involvement of superoxide, was controversial. The stoichiometry of the reaction has now been established using nitrate ion electrode and a methemoglobin free radical was detected by ESR during the oxidation. Complete inhibition of the autocatalysis by aniline or aminopyrine suggests that the radical catalyzes conversion of nitrite to NO2, which oxidizes oxyhemoglobin. Recently NO was shown to be one of endothelium-derived relaxing factors and the relaxation induced by the factor was inhibited by hemoglobin and potentiated by superoxide dismutase.
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PMID:The interaction between nitrogen oxides and hemoglobin and endothelium-derived relaxing factor. 255 83

It was detected that both NAD(P)H-linked reductase (TNT-Red) and NAD(P)+-linked TNT dehydrogenase (TNT-Deh) were present in TNT-degrading enzymes of Citrobacter freundii simultaneously. The time course of formation for the enzymes and the actions of coenzymes in enzymatic reaction of TNT have been studied. The effects of varied carbon and nitrogen sources on the regulation of the enzymes were different clearly. When the concentration of NH4Cl or urea in culture medium was more than 0.1 mol/L, the formation of both TNT reductase and TNT dehydrogenase was promoted. However, the formation of these enzymes was inhibited by KNO3 in culture. The production of both reductase and dehydrogenase was promoted by glucose. The sodium citrate was able to help the formation of the TNT dehydrogenase. The activity of the TNT reductase was increased when the concentration of sodium citrate was less than 0.5%, but when it was more than 0.5%, the activity of this enzyme was decreased rapidly.
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PMID:[TNT-degrading enzyme of Citrobacter freundii and its regulation by carbon and nitrogen source]. 280 May 43


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