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)

Ultraviolet light was shown to inactivate purified nitrate reductase in the presence of reduced benzyl viologen. Loss of activity was not complete, reaching 60 to 70%. Photolysis was maximum at 345 nm. The differential spectrum between native and irradiated enzyme exhibited absorption bands at 216, 275, 314 and 365 nm. The photosensitive electron carrier could be extracted by organic solvents. It had the following absorption bands: 225, 275 and 285 nm. It was reduced by Nile blue A but not by methylene blue. The precise nature of this light sensitive molecule could not be determined although the results support the idea that this chromophore might be a naphthoquinone.
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PMID:An ultraviolet light sensitive target in nitrate reductase of Escherichia coli K-12. 332 2

On the basis of the observation that nitrate reductase from Escherichia coli is sensitive to UV irradiation with an action spectrum indicative of a naphthoquinone (F. Brito and M. Dubourdieu, Biochem. Int. 15:1079-1088, 1987), we extracted and characterized quinone components from two different preparations of purified nitrate reductase. A soluble form of nitrate reductase, composed of alpha and beta subunits, was purified after release from the membrane fraction by heat treatment, and a detergent-solubilized form, containing alpha, beta, and gamma (cytochrome bNR) subunits, was purified in the presence of Triton X-100. Extraction of soluble alpha beta form with chloroform-methanol yielded several UV-absorbing components, which were characterized as menaquinone-9 with an oxidized side chain and further photodestruction products of the menaquinone. The total amount of menaquinone extracted into the organic phase was estimated to be 0.97 mol/mol of alpha beta dimer. Extraction of the detergent-solubilized alpha beta gamma form by a similar procedure yielded two naphthoquinone-like components which were characterized by mass spectrometry as the oxidized forms of menaquinone-9 and demethylmenaquinone-9. In this case, the molar ratio of total naphthoquinone to the alpha beta dimer was estimated to be greater than 6:1. When cytochrome bNR and detergent were eliminated from the detergent-solubilized enzyme by heat treatment and ion-exchange chromatography, only menaquinone-9 could be identified in the organic extract of the active alpha beta product. These results suggest that menaquinone-9 is specifically bound to the alpha beta dimer and may be the UV-sensitive component in the pathway of electron transfer catalyzed by nitrate reductase.
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PMID:Isolation and identification of menaquinone-9 from purified nitrate reductase of Escherichia coli. 760 37

Magnetic switching of redox reactions and bioelectrocatalytic transformations is accomplished in the presence of relay-functionalized magnetite particles (Fe(3)O(4)). The electrochemistry of a naphthoquinone (1), pyrroloquinoline quinone (2; PQQ), microperoxidase-11 (3), a ferrocene derivative (4) and a bipyridinium derivative (5), functionalized magnetic particles, is switched "ON" and "OFF" by an external magnet upon the attraction of the magnetic particles to an electrode or their retraction from the electrode, respectively. The magneto-switchable activation and deactivation of the electrochemical oxidation of the ferrocene-functionalized magnetic particles and the electrochemical reduction of the bipyridinium-functionalized magnetic particles are used for the triggering of mediated bioelectrocatalytic oxidation of glucose, in the presence of glucose oxidase (GOx), and bioelectrocatalytic reduction of nitrate (NO(3) (-)), in the presence of nitrate reductase (NR), respectively. Magnetic particles functionalized with a PQQ-NAD(+) dyad are used for the magnetic switching of the bioelectrocatalytic oxidation of lactate in the presence of lactate dehydrogenase (LDH). The coupling of these particles with a ferrocene-monolayer-functionalized electrode allows the dual and selective sensing of lactate and glucose in the presence of LDH and GOx, respectively, by using an external magnet to switch the detection mode.
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PMID:Magneto-switchable electrocatalytic and bioelectrocatalytic transformations. 1229 4

Nap (periplasmic nitrate reductase) operons of many bacteria include four common, essential components, napD, napA, napB and napC (or a homologue of napC ). In Escherichia coli there are three additional genes, napF, napG and napH, none of which are essential for Nap activity. We now show that deletion of either napG or napH almost abolished Nap-dependent nitrate reduction by strains defective in naphthoquinone synthesis. The residual rate of nitrate reduction (approx. 1% of that of napG+ H+ strains) is sufficient to replace fumarate reduction in a redox-balancing role during growth by glucose fermentation. Western blotting combined with beta-galactosidase and alkaline phosphatase fusion experiments established that NapH is an integral membrane protein with four transmembrane helices. Both the N- and C-termini as well as the two non-haem iron-sulphur centres are located in the cytoplasm. An N-terminal twin arginine motif was shown to be essential for NapG function, consistent with the expectation that NapG is secreted into the periplasm by the twin arginine translocation pathway. A bacterial two-hybrid system was used to show that NapH interacts, presumably on the cytoplasmic side of, or within, the membrane, with NapC. As expected for a periplasmic protein, no NapG interactions with NapC or NapH were detected in the cytoplasm. An in vitro quinol dehydrogenase assay was developed to show that both NapG and NapH are essential for rapid electron transfer from menadiol to the terminal NapAB complex. These new in vivo and in vitro results establish that NapG and NapH form a quinol dehydrogenase that couples electron transfer from the high midpoint redox potential ubiquinone-ubiquinol couple via NapC and NapB to NapA.
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PMID:NapGH components of the periplasmic nitrate reductase of Escherichia coli K-12: location, topology and physiological roles in quinol oxidation and redox balancing. 1467 86