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 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.

Characterization of phenolic ionizations in horse heart cytochrome c

Biochemistry ◽  
1984 ◽  
Vol 23 (26) ◽  
pp. 6649-6654
Author(s):  
G. E. Marti ◽  
M. A. Marini ◽  
B. R. Sreenathan
Keyword(s):  
Cytochrome C ◽  
Horse Heart Cytochrome ◽  
Horse Heart Cytochrome C

scholarly journals Spectroscopic, Structural, and Functional Characterization of the Alternative Low-Spin State of Horse Heart Cytochrome c

2008 ◽  
Vol 94 (10) ◽  
pp. 4066-4077 ◽  
Author(s):  
Katia C.U. Mugnol ◽  
Rômulo A. Ando ◽  
Rafael Y. Nagayasu ◽  
Adelaide Faljoni-Alario ◽  
Sergio Brochsztain ◽  
...  
Keyword(s):  
Cytochrome C ◽  
Spin State ◽  
Functional Characterization ◽  
Horse Heart Cytochrome ◽  
Horse Heart Cytochrome C

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

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.

Kinetics and mechanism of the reaction between oxidized cytochrome c and ascorbic acid

1991 ◽  
Vol 56 (2) ◽  
pp. 478-490 ◽  
Author(s):  
Joaquin F. Perez-Benito ◽  
Conchita Arias
Keyword(s):  
Ascorbic Acid ◽  
Cytochrome C ◽  
Redox Reactions ◽  
Arrhenius Equation ◽  
Horse Heart Cytochrome ◽  
First Order ◽  
Acidic Form ◽  
Ph Range ◽  
Horse Heart Cytochrome C ◽  
Mechanism Of The Reaction

The reaction between horse-heart cytochrome c and ascorbic acid has been investigated in the pH range 5.5 – 7.1 and at 10.0 – 25.0 °C. The rate shows a first-order dependence on the concentration of cytochrome c, it increases in a non-linear way as the concentration of ascorbic acid increases, it increases markedly with increasing pH and, provided that the ionic strength of the medium is high enough, it fulfills the Arrhenius equation. The apparent activation energy increases as the pH of the solution increases. The results have been explained by means of a mechanism that includes the existence of an equilibrium between two forms (acidic and basic) of oxidized cytochrome c: cyt-H+ -Fe3+ + OH- cyt -Fe3+ + H2O, whose equilibrium constant is (6.7 ± 1.4). 108 at 25.0 °C, the acidic form being more reducible than the basic one. It is suggested that there is a linkage of hydrogenascorbate ion to both forms of cytochrome c previous to the redox reactions. Two possibilities for the oxidant-reductant linkage (binding and adsorption) are discussed in detail.

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