Bacterial nitrite-reducing enzymes

Brittain, Thomas; Blackmore, Richard S.; Greenwood, C. T.; Thomson, Andrew J.

doi:10.1007/978-3-642-78046-2_19

Cited by 18 publications

(23 citation statements)

References 136 publications

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“…An EPR signal with even higher g, , , at 3.81 was observed for the ammoniaforming nitrite reductase from 5'. deleyianum (Schumacher and Kroneck, 1991) and from other microorganisms (Brittain et al, 1992). Heme-heme interaction was proposed to explain the unusual EPR feature observed in these multiheme nitrite reductases.…”

Section: Spectroscopic Propertiesmentioning

confidence: 99%

Nitric oxide reductase from Pseudomonas stutzeri, a novel cytochrome bc complex

Kastrau¹,

Heiss²,

Kroneck³

et al. 1994

European Journal of Biochemistry

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The nitric oxide reductase (NOR) from Pseudomonas stutzeri is a cytochrome bc complex which shows on SDSPAGE two subunits with apparent molecular masses of 17 kDa and 38 kDa. Two other species of =45 kDa and 74-78 kDa represent the undissociated enzyme complex and an aggregate of the cytochrome b subunit, respectively. The cytochrome b subunit is highly hydrophobic and results in aberrant electrophoretic mobility. The stability of the enzyme in various detergents and at different pH was investigated. The highest specific activity of 60 pmol NO min-' mg-' protein was obtained after electrophoresis in the presence of laurylpropanediol-3-phosphorylcholine ether. Purified NOR contained cardiolipin, phosphatidylglycerol, and phosphatidylethanolamine, the latter as the major component. A phospholipid was required for high catalytic activity with either cardiolipin or phospatidylglycerol increasing the activity of the enzyme as isolated by a factor of up to 5. Free fatty acids inhibited NOR, with cis-9-octadecenoic acid (oleic acid) showing the most pronounced effect. Certain detergents substituted for the phospholipid requirement of NOR.The enzyme, as isolated, in 0.1% Triton X-100, 20 mM Tris/HCl pH 8.5, exhibited a complex set of EPR resonances at low magnetic field, with a prominent peak at g 6.34 resulting from Fe(II1) high-spin cytochrome b. The second prominent feature arose from a low-spin Fe(II1) heme center with strong lines at apparent g values of 3.02 and 2.29, and a broad resonance at g= 1.5 which we assigned to the cytochrome c component of the enzyme. From spin quantitation and computer simulations of the various EPR signals a ratio close to 1 : 1 for the low-spinhigh-spin heme centers in NOR was estimated. Shifting the pH from 8.5 to 5.0, replacing Triton X-100 by other detergents, or adding soybean phospholipids to the protein, led to pronounced changes of the EPR signals in the g = 6 region. In contrast, the strong inhibitor oleic acid did not cause significant spectral changes. NOR which had been reduced by L-ascorbate/phenazine methosulfate prior to incubation with its substrate NO gave the characteristic Fe(I1) nitrosyl triplet centered at g = 2.01, with a hyperfine splitting of 1.70 mT. In the absence of dioxygen, NOR was quantitatively reduced by either sodium dithionite, or photochemically with deazaflavin and oxalate ; the enzyme was reoxidizable by ferricyanide in a fully reversible reaction. Spectroelectrochemical oxidoreductive titrations gave EA (versus standard hydrogen electrode) = +322 mV for the cytochrome b and +280 mV for the cytochrome c component. NO-reducing activities have been found in a large variety of bacteria, but so far the enzyme has been partially characCorrespondence to P. M. H. Kroneck,

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Section: Spectroscopic Propertiesmentioning

confidence: 99%

Nitric oxide reductase from Pseudomonas stutzeri, a novel cytochrome bc complex

Kastrau¹,

Heiss²,

Kroneck³

et al. 1994

European Journal of Biochemistry

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“…Lastly, disruption of the NsrR repressor divergently encoded upstream of the nirK gene cluster resulted in constitutive expression of NirK (2). Together, these results suggest that nirK and the three genes in its cluster are negatively regulated as an operon by NsrR to aerobically detoxify NO 2 Ϫ produced by N. europaea during ammonia oxidation rather than to anaerobically reduce NO 2 Ϫ as is typical for NirK-like enzymes in denitrifying bacteria (6).…”

mentioning

confidence: 76%

Transcriptome of a Nitrosomonas europaea Mutant with a Disrupted Nitrite Reductase Gene ( nirK )

Cho

Tao

Liu

et al. 2006

Appl Environ Microbiol

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Global gene expression was compared between the Nitrosomonas europaea wild type and a nitrite reductasedeficient mutant using a genomic microarray. Forty-one genes were differentially regulated between the wild type and the nirK mutant, including the nirK operon, genes for cytochrome c oxidase, and seven iron uptake genes. Relationships of differentially regulated genes to the nirK mutant phenotype are discussed.

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“…In this context it must be kept in mind that NO itself is not toxic to many bacteria, as certain enteric bacteria contain nitrate reductase and produce NO on their own. 37 Importantly, however, as observed in septic patients, epithelial iNOS induction and NO production may cause increased intestinal permeability. 38 Indeed, selective inhibition of iNOS in endotoxemic rats ameliorated mucosal permeability for dextran (MW 4000) 39 and reduced bacterial translocation.…”

Section: Discussionmentioning

confidence: 99%