scholarly journals Oxidation of nicotinamide coenzyme dimers by one-electron-accepting proteins

1986 ◽  
Vol 237 (3) ◽  
pp. 919-922 ◽  
Author(s):  
L Avigliano ◽  
V Carelli ◽  
A Casini ◽  
A Finazzi-Agrò ◽  
F Liberatore ◽  
...  
Keyword(s):  
Superoxide Dismutase ◽  
Cytochrome C ◽  
Electrochemical Reduction ◽  
Electron Acceptors ◽  
Single Electron ◽  
Redox Mechanism ◽  
Cytochrome C Reductase ◽  
Nicotinamide Coenzymes ◽  
Nadh Cytochrome ◽  
Phenazine Methosulphate

The nicotinamide nucleotide dimers (NAD)2 and (NADP)2, obtained by electrochemical reduction of NAD+ and NADP+, are able to reduce such single-electron acceptors as the proteins cytochrome c, azurin and methaemoglobin, though at different rates. Under the same conditions the reduced nicotinamide coenzymes NADH and NADPH are not able to reduce these proteins at measurable rates unless a catalyst (phenazine methosulphate or NADH-cytochrome c reductase in the case of cytochrome) is present. The redox mechanism seems to involve the formation of an NAD(P). radical that in the presence of O2 gives rise to superoxide (O2.-), since superoxide dismutase inhibited these reactions.

scholarly journals Properties of a cytochrome c-enriched light particulate fraction isolated from the photosynthetic bacterium Rhodopseudomonas spheroides

1978 ◽  
Vol 174 (1) ◽  
pp. 267-275 ◽  
Author(s):  
J Barrett ◽  
C N Hunter ◽  
O T G Jones
Keyword(s):  
Cytochrome C ◽  
Sodium Dodecyl ◽  
Photosynthetic Bacterium ◽  
Particulate Fraction ◽  
Cytochrome C Reductase ◽  
Cytochrome C2 ◽  
Succinate Cytochrome C Reductase ◽  
Bulk Membrane ◽  
Nadh Cytochrome ◽  
Rhodopseudomonas Spheroides

Differential centrifugation of suspensions of French-press-disrupted Rhodopseudomonas spheroides yielded a light particulate fraction that was different in many properties from the bulk membrane fraction. It was enriched in cytochrome c and had a low cytochrome b content. When prepared from photosynthetically grown cells this fraction had a very low specific bacteriochlorophyll content. The cytochrome c of the light particles differed in absorption maxima at 77K from cytochrome c2 attached to membranes; there was pronounced splitting of the alpha-band, as is found in cytochrome c2 free in solution. Potentiometric titration at A552–A540 showed the presence of two components that fitted an n = 1 titration; one component had a midpoint redox potential of +345mV, like cytochrome c2 in solution, and the second had E0′ at pH 7.0 of +110 mV, and they were present in a ratio of approx. 2:3. Difference spectroscopy at 77K showed that the spectra of the two components were very similar. More of a CO-binding component was present in particles from photosynthetically grown cells. Light membranes purified by centrifugation on gradients of 5–60% (w/w) sucrose retained the two c cytochromes; they contained no detectable succinate-cytochrome c reductase or bacteriochlorophyll and very little ubiquinone, but they contained NADH-cytochrome c reductase and some phosphate. Electrophoresis on sodium dodecyl sulphate/polyacrylamide gels showed that the light membranes of aerobically and photosynthetically grown cells were very similar and differed greatly from other membrane fractions of R. spheroides.

Endoplasmic reticulum membrane isolated from small-intestinal epithelial cells: enzyme and protein components

1981 ◽  
Vol 52 (1) ◽  
pp. 215-222
Author(s):  
M. Fujita ◽  
H. Ohta ◽  
T. Uezato
Keyword(s):  
Endoplasmic Reticulum ◽  
Epithelial Cells ◽  
Cytochrome C ◽  
Endoplasmic Reticulum Membrane ◽  
Dependent Manner ◽  
Cytochrome C Reductase ◽  
Basolateral Membranes ◽  
Nadh Cytochrome ◽  
Protein Components ◽  
A Minor

Endoplasmic reticulum membrane-rich fraction was obtained by subfractionation of the light microsomes from mouse jejunal mucosal epithelial cells. It was marked by high glucose-6-phosphatase, NADPH-cytochrome c reductase, and NADH-cytochrome c reductase activities and low Na+,K+-ATPase activity. The enrichment of Na+,K+-ATPase was 180-fold higher in the basolateral membranes than in the endoplasmic reticulum membrane-rich fraction relative to glucose-6-phosphatase. The protein peak that was phosphorylated in a Na-dependent manner was prominent in the basolateral membranes while it was a minor peak in the endoplasmic reticulum membrane-rich fraction. Under the electron microscope the fraction was seen to be composed of homogeneous small vesicles with thin smooth membranes.

Ferrocyanide-activated NADH cytochrome c reductase from barley

1980 ◽  
Vol 18 (4) ◽  
pp. 389-393 ◽  
Author(s):  
Ian S. Small ◽  
John L. Wray
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Reductase ◽  
Nadh Cytochrome

Brain Regional Analysis of NADH-Cytochrome C Reductase Activity in Alzheimerʼs Disease

1990 ◽  
Vol 49 (3) ◽  
pp. 206-214 ◽  
Author(s):  
GEORGE S. ZUBENKO ◽  
JOHN MOOSSY ◽  
DIANA CLAASSEN ◽  
A. Julio Martinez ◽  
GUTTI R. RAO
Keyword(s):  
Cytochrome C ◽  
Reductase Activity ◽  
Regional Analysis ◽  
Cytochrome C Reductase ◽  
Nadh Cytochrome

Acute inhibition of respiratory capacity of muscle reduces peak oxygen consumption

1990 ◽  
Vol 259 (6) ◽  
pp. C889-C896 ◽  
Author(s):  
R. M. McAllister ◽  
R. L. Terjung
Keyword(s):  
Oxygen Consumption ◽  
Electron Transport ◽  
Cytochrome C ◽  
Peak Oxygen Consumption ◽  
Dependent Manner ◽  
Cytochrome C Reductase ◽  
Energy Demands ◽  
Hindlimb Muscle ◽  
Nadh Cytochrome

Electron transport capacity of skeletal muscle was inhibited in situ in an acute dose-dependent manner with myxothiazol, a tight-binding inhibitor of ubiquinone-cytochrome c reductase, complex III of the respiratory chain. Peak oxygen consumption of rat hindlimb muscle was determined via consecutive 10-min isometric contraction (100 ms at 100 Hz) periods of increasing energy demands (4, 8, 15, 30, 45, and 60 tetani/min), using an isolated hindlimb preparation perfused with a high oxygen delivery (approximately 6-8 mumol.min-1.g-1). Peak oxygen consumption decreased from 4.61 +/- 0.19 mumol.min-1.g-1 (control) in a dose-dependent manner to 0.73 +/- 0.07 mumol.min-1.g-1 at 0.50 microM myxothiazol in blood. Oxygen extraction decreased from 65 to 12% of delivered oxygen. Furthermore, the reduction in peak respiratory rate became evident at lower energy demands of the contraction sequence. Myxothiazol inhibition of respiration was not dependent on the presence of muscle contractions but was evident when mitochondria were uncoupled with carbonyl cyanide m-chlorophenylhydrazone. A 50% effective dosage (ED50) of 0.21 microM myxothiazol for inhibition of peak oxygen consumption closely resembled the inhibition of NADH-cytochrome c reductase activity (ED50 of 0.27 microM) determined from homogenates of the same muscles. This suggests that the peak oxygen consumption of skeletal muscle is tightly coupled to the capacity for electron transport evaluated by flux through NADH-cytochrome c reductase. If the enzyme activity measured in vitro correctly represents available enzymatic capacity within contracting muscle, approximately 75% of electron transport capacity for handling reducing equivalents generated from NADH is utilized during peak oxygen consumption of rat hindlimb muscle contracting in situ.

scholarly journals Structural and functional relationships of enzyme activities induced by nitrate in barley

1970 ◽  
Vol 119 (4) ◽  
pp. 715-725 ◽  
Author(s):  
John L. Wray ◽  
Philip Filner
Keyword(s):  
Cytochrome C ◽  
Nitrate Reductase ◽  
Nitrate Reductase Activity ◽  
Reductase Activity ◽  
Bottom Layer ◽  
Sucrose Density Gradient ◽  
Enzyme Complex ◽  
Cytochrome C Reductase ◽  
Functional Relationships ◽  
Nadh Cytochrome

1. Nitrate induces the development of NADH-nitrate reductase (EC 1.6.6.1), FMNH2–nitrate reductase and NADH–cytochrome c reductase activities in barley shoots. 2. Sucrose-density-gradient analysis shows one band of NADH–nitrate reductase (8S), one band of FMNH2–nitrate reductase activity (8S) and three bands of NADH–cytochrome c reductase activity (bottom layer, 8S and 3.7S). Both 8S and 3.7S NADH–cytochrome c reductase activities are inducible by nitrate, but the induction of the 8S band is much more marked. 3. The 8S NADH–cytochrome c reductase band co-sediments with both NADH–nitrate reductase activity and FMNH2–nitrate reductase activity. Nitrite reductase activity (4.6S) did not coincide with the activity of either the 8S or the 3.7S NADH–cytochrome c reductase. 4. FMNH2–nitrate reductase activity is more stable (t½ 12.5min) than either NADH–nitrate reductase activity (t½ 0.5min) or total NADH–cytochrome c reductase activity (t½ 1.5min) at 45°C. 5. NADH–cytochrome c reductase and NADH–nitrate reductase activities are more sensitive to p-chloromercuribenzoate than is FMNH2–nitrate reductase activity. 6. Tungstate prevents the formation of NADH–nitrate reductase and FMNH2–nitrate reductase activities, but it causes superinduction of NADH–cytochrome c reductase activity. Molybdate overcomes the effects of tungstate. 7. The same three bands (bottom layer, 8S and 3.7S) of NADH–cytochrome c reductase activity are observed irrespective of whether induction is carried out in the presence or absence of tungstate, but only the activities in the 8S and 3.7S bands are increased. 8. The results support the idea that NADH–nitrate reductase, FMNH2–nitrate reductase and NADH–cytochrome c reductase are activities of the same enzyme complex, and that in the presence of tungstate the 8S enzyme complex is formed but is functional only with respect to NADH–cytochrome c reductase activity.

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