scholarly journals Nitric and nitrous oxide reductases are active under aerobic conditions in cells of Thiosphaera pantotropha

1991 ◽  
Vol 273 (2) ◽  
pp. 423-427 ◽  
Author(s):  
L C Bell ◽  
S J Ferguson
Keyword(s):  
Nitrous Oxide ◽  
Reductase Activity ◽  
Nitrous Oxide Reductase ◽  
Nitric Oxide Reductase ◽  
Mutual Inhibition ◽  
Horse Heart Cytochrome ◽  
Aerobic Conditions ◽  
Thiosphaera Pantotropha ◽  
Horse Heart Cytochrome C ◽  
In Cells

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.

scholarly journals The nitric oxide reductase of Paracoccus denitrificans

1990 ◽  
Vol 269 (2) ◽  
pp. 423-429 ◽  
Author(s):  
G J Carr ◽  
S J Ferguson
Keyword(s):  
Nitric Oxide ◽  
Specific Activity ◽  
Paracoccus Denitrificans ◽  
Reductase Activity ◽  
Cytochrome Bc1 Complex ◽  
Horse Heart Cytochrome ◽  
Dodecyl Maltoside ◽  
Solubilized Enzyme ◽  
Horse Heart Cytochrome C ◽  
Good Retention

The nitric oxide (NO) reductase activity of the cytoplasmic membrane of Paracoccus denitrificans can be solubilized in dodecyl maltoside with good retention of activity. The solubilized enzyme lacks NADH-dependent activity, but can be assayed with isoascorbate plus 2,3,5,6-tetramethylphenylene-1,4-diamine as electron donor and with horse heart cytochrome c as mediator. Reduction of NO was measured with an amperomeric electrode. The solubilized enzyme could be separated from other electron-transport components, including the cytochrome bc1 complex and nitrite reductase, by several steps of chromatography. The purified enzyme had a specific activity of 11 mumols.min-1.mg of protein-1 and the Km(NO) was estimated as less than 10 microM. The enzyme formed N2O from NO with the expected stoichiometry. These observations support the view that NO reductase is a discrete enzyme that participates in the denitrification process. The enzyme contained both b- and c-type haems. The former was associated with a polypeptide of apparent molecular mass 37 kDa and the latter with a polypeptide of 18 kDa. Polypeptides of 29 and 45 kDa were also identified in the purified protein which showed variable behaviour on electrophoresis in polyacrylamide gels.

scholarly journals Characterization of the second prosthetic group of the flavoenzyme NADH–acceptor reductase (component C) of the methane mono-oxygenase from Methylococcus capsulatus (Bath)

1979 ◽  
Vol 177 (3) ◽  
pp. 903-908 ◽  
Author(s):  
J Colby ◽  
H Dalton
Keyword(s):  
Reductase Activity ◽  
Methylococcus Capsulatus ◽  
Prosthetic Group ◽  
Horse Heart Cytochrome ◽  
Oxygenase Activity ◽  
Component C ◽  
Hexamethyl Phosphoramide ◽  
Horse Heart Cytochrome C ◽  
Acid Labile

1. A new two-step purification is described that routinely yields 100mg quantities of component C for biochemical studies. 2. Chemical analyses show component C purified by this procedure to contain 2 g-atoms of iron, 2 mol of acid-labile sulphide (S) and 1 mol of FAD per mol of protein. 3. The Fe-S core of component C was extruded by treating the protein with p-methoxybenzenethiol in hexamethyl phosphoramide/50mM-Tris/HCl buffer, pH 8.5 (4:1, v/v), under anaerobic conditions. The spectral properties of the extruded core suggest that component C contains 1 mol of [2Fe-2S(S-Cys)4] centre per mol of protein. 4. E.p.r. spectroscopy confirms the presence of a Fe-S centre in component C. 5. Component C catalyses the reduction by NADH of ferricyanide, 2,6-dichlorophenol-indophenol or horse heart cytochrome c, with specific activities of 50–230 units/mg of protein. 6. The optimum pH for the NADH-acceptor reductase activity is 8.5–9.0, and the apparent Km values for NADH and NADPH are 0.05mM and 15.5mM respectively. 7. Unlike methane mono-oxygenase activity, NADH-acceptor reductase activity of component C is not inhibited by 8-hydroxyquinoline or by acetylene.

scholarly journals Symbiotic Bradyrhizobium japonicum Reduces N2O Surrounding the Soybean Root System via Nitrous Oxide Reductase

2006 ◽  
Vol 72 (4) ◽  
pp. 2526-2532 ◽  
Author(s):  
Reiko Sameshima-Saito ◽  
Kaori Chiba ◽  
Junta Hirayama ◽  
Manabu Itakura ◽  
Hisayuki Mitsui ◽  
...  
Keyword(s):  
Nitrous Oxide ◽  
Root System ◽  
Bradyrhizobium Japonicum ◽  
Reductase Activity ◽  
Ambient Air ◽  
Living Cells ◽  
Nitrous Oxide Reductase ◽  
Free Living ◽  
Low Concentrations ◽  
Soybean Roots

ABSTRACT N2O reductase activity in soybean nodules formed with Bradyrhizobium japonicum was evaluated from N2O uptake and conversion of 15N-N2O into 15N-N2. Free-living cells of USDA110 showed N2O reductase activity, whereas a nosZ mutant did not. Complementation of the nosZ mutant with two cosmids containing the nosRZDFYLX genes of B. japonicum USDA110 restored the N2O reductase activity. When detached soybean nodules formed with USDA110 were fed with 15N-N2O, they rapidly emitted 15N-N2 outside the nodules at a ratio of 98.5% of 15N-N2O uptake, but nodules inoculated with the nosZ mutant did not. Surprisingly, N2O uptake by soybean roots nodulated with USDA110 was observed even in ambient air containing a low concentration of N2O (0.34 ppm). These results indicate that the conversion of N2O to N2 depends exclusively on the respiratory N2O reductase and that soybean roots nodulated with B. japonicum carrying the nos genes are able to remove very low concentrations of N2O.

The multicopper oxidase from the archaeon Pyrobaculum aerophilum shows nitrous oxide reductase activity

FEBS Journal ◽  
2010 ◽  
Vol 277 (15) ◽  
pp. 3176-3189 ◽  
Author(s):  
André T. Fernandes ◽  
João M. Damas ◽  
Smilja Todorovic ◽  
Robert Huber ◽  
M. Camilla Baratto ◽  
...  
Keyword(s):  
Nitrous Oxide ◽  
Reductase Activity ◽  
Multicopper Oxidase ◽  
Nitrous Oxide Reductase ◽  
Pyrobaculum Aerophilum

Probing the nitrite and nitric oxide reductase activity of cbb3 oxidase: resonance Raman detection of a six-coordinate ferrous heme–nitrosyl species in the binuclear b3/CuB center

2015 ◽  
Vol 51 (98) ◽  
pp. 17398-17401 ◽  
Author(s):  
Andreas Loullis ◽  
Eftychia Pinakoulaki
Keyword(s):  
Nitric Oxide ◽  
Nitrous Oxide ◽  
Reductase Activity ◽  
Resonance Raman ◽  
Nitric Oxide Reductase ◽  
Ferrous Heme

We present resonance Raman and FTIR evidence for the reduction of nitrite to nitrous oxide by cbb3 oxidase through the formation of a ferrous six-coordinate heme b3–nitrosyl species.

Cardiolipin modulates allosterically the nitrite reductase activity of horse heart cytochrome c

2014 ◽  
Vol 19 (7) ◽  
pp. 1195-1201 ◽  
Author(s):  
Paolo Ascenzi ◽  
Maria Marino ◽  
Fabio Polticelli ◽  
Roberto Santucci ◽  
Massimo Coletta
Keyword(s):  
Cytochrome C ◽  
Nitrite Reductase ◽  
Reductase Activity ◽  
Horse Heart Cytochrome ◽  
Nitrite Reductase Activity ◽  
Horse Heart Cytochrome C
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