Electron Transport and Coupled Energy Generation in Pseudomonas saccharophila

1971 ◽  
Vol 49 (11) ◽  
pp. 1175-1182 ◽  
Author(s):  
M. Ishaque ◽  
A. Donawa ◽  
M. I. H. Aleem
Keyword(s):  
Oxygen Consumption ◽  
Electron Transport ◽  
Cytochrome C ◽  
Atp Synthesis ◽  
Succinate Oxidation ◽  
Atp Formation ◽  
Low Concentrations ◽  
Oxidase Enzyme ◽  
Succinate Oxidase ◽  
Pseudomonas Saccharophila

The respiratory chain system of heterotrophically grown Pseudomonas saccharophila contained cytochromes of the b, c, a, and o types and also the NADH and succinate oxidase enzyme systems. Cell-free extracts catalyzed phosphorylation coupled to the oxidation of NADH, succinate, and ascorbate (plus cytochrome c). The P/O ratios were in the range of 1.00 for generated NADH, 0.29 for added NADH, 0.50 for succinate, and 0.25 for ascorbate (plus cytochrome c).The oxidative phosphorylation was uncoupled by 2,4-dinitrophenol, 2,6-dibromophenol, pentachlorophenol, m-chlorocarbonyl cyanide phenylhydrazone, and dicumarol without any inhibition of oxygen consumption. Phosphorylation coupled to NADH oxidation was completely inhibited by the flavoprotein inhibitors such as rotenone, amytal, and atabrine; these inhibitors had no effect, however, on the ATP synthesis associated with succinate oxidation. Antimycin A or 2-n-nonyl-4-hydroxyquinoline-N-oxide as well as cyanide or azide at low concentrations completely inhibited the phosphate esterification coupled to the oxidation of NADH or succinate, but had little or no effect on the oxygen consumption. Relatively higher concentrations of oligomycin were required for a complete inhibition of the electron-transport-linked ATP formation.

Comparative studies on succinate and terminal oxidase activity in microbial and mammalian electron-transport systems

1969 ◽  
Vol 15 (7) ◽  
pp. 797-807 ◽  
Author(s):  
Peter Jurtshuk ◽  
Ann K. May ◽  
Leodocia M. Pope ◽  
Patricia R. Aston
Keyword(s):  
Electron Transport ◽  
Cytochrome C ◽  
Comparative Studies ◽  
Azotobacter Vinelandii ◽  
Transport Systems ◽  
Terminal Oxidase ◽  
Succinate Oxidation ◽  
State Reduction ◽  
Hydroxy Quinoline ◽  
Terminal Oxidation

A comparative study was undertaken to examine the succinate and terminal oxidase activities of the electron-transport systems of Azotobacter vinelandii and mammalian mitochondria. For succinate oxidation, both systems exhibited similar relative specificities for the electron acceptors phenazine methosulfate, O2, methylene blue, K3Fe(CN)6, nitrotetrazolium blue, 2,6-dichlorophenolindophenol (DCIP), and cytochrome c. They differed in that DCIP and cytochrome c were less active in the Azotobacter electron-transport system (R3 fraction) than in the bovine mitochondrial system. Comparative studies with known inhibitors of mammalian mitochondrial electron-transport demonstrated that the succinoxidase activity of the Azotobacter R3 fraction was, at least, 2000 times less sensitive to antimycin A, 700 times less sensitive to thenoyl-trifluoroacetone, and 30 times less sensitive to 2-n-heptyl-4-hydroxy-quinoline-N-oxide. Both systems were equally sensitive to KCN, p-chloromercuribenzoic acid, and chlorpromazine.The ability of the two systems to use tetramethyl-p-phenylenediamine (TMPD) and its derivatives as electron donors, for terminal oxidation, was also similar. Studies on steady state reduction revealed that in the Azotobacter R3 fraction, the cytochromes (a2, a1, b1, c4 + c5) and flavoprotein components were reduced substantially by succinate as well as by TMPD in the presence of ascorbate. Ultrastructure analyses of the Azotobacter R3 electron-transport fraction revealed the vesicular membranous components identified as oxidosomes according to the terminology used by DeLey and contained spherical headpiece units of 80 Å in diameter which appeared to be morphologically identical with the tripartite units or the elementary particles described by Green and associates, viz., Kopaczyk et al., and by Fernandez-Moran et al.

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.

Ultrastructural Cytochemistry of Some Oxidative Enzymes

1974 ◽  
Vol 32 ◽  
pp. 322-323
Author(s):  
Arnold M. Seligman
Keyword(s):  
Electron Transport ◽  
Cytochrome C ◽  
Succinic Dehydrogenase ◽  
Atp Synthesis ◽  
Oxidative Enzymes ◽  
Reaction Products ◽  
Inner Mitochondrial Membrane ◽  
Design And Synthesis ◽  
Membrane Bound ◽  
Membrane Bound Enzymes

The membrane-bound enzymes of the succinic oxidase chain of electron transport on the cristae of mitochondria have been the target of ultrastructural cytochemical research for a number of years. Methods for succinic dehydrogenase have been improved by the continuous design and synthesis of better tetrazolium salts. The most recent is BSPT, which is not osmiophilic, but yields an osmiophilic, lipophobic, insoluble formazan. The terminal triplet of the chain of electron transport or cytochrome oxidase, consisting of cytochrome c, a and a3 has been demonstrated very well via cytochrome c with diaminobenzidine (DAB). The localization of these two reaction products specifically on the outer surface of the inner mitochondrial membrane, lends some support to speculation concerning the mechanism of transfer of oxidative energy for ATP synthesis.

scholarly journals Idebenone-Induced Recovery of Glycerol-3-Phosphate and Succinate Oxidation Inhibited by Digitonin

2012 ◽  
pp. 259-265 ◽  
Author(s):  
H. RAUCHOVÁ ◽  
M. VOKURKOVÁ ◽  
Z. DRAHOTA
Keyword(s):  
Oxygen Consumption ◽  
Cytochrome C ◽  
Oxidation Rate ◽  
Mitochondrial Membrane ◽  
Synthetic Analog ◽  
Active Components ◽  
Inner Mitochondrial Membrane ◽  
Succinate Oxidation ◽  
Consumption Rates ◽  
Cyt C

Digitonin solubilizes mitochondrial membrane, breaks the integrity of the respiratory chain and releases two mobile redox-active components: coenzyme Q (CoQ) and cytochrome c (cyt c). In the present study we report the inhibition of glycerol-3-phosphate- and succinate-dependent oxygen consumption rates by digitonin treatment. Our results show that the inhibition of oxygen consumption rates is recovered by the addition of exogenous synthetic analog of CoQ idebenone (hydroxydecyl-ubiquinone; IDB) and cyt c. Glycerol-3-phosphate oxidation rate is recovered to 148 % of control values, whereas succinate-dependent oxidation rate only to 68 %. We find a similar effect on the activities of glycerol-3-phosphate and succinate cytochrome c oxidoreductase. Our results also indicate that succinate-dependent oxidation is less sensitive to digitonin treatment and less activated by IDB in comparison with glycerol-3-phosphate-dependent oxidation. These findings might indicate the different mechanism of the electron transfer from two flavoprotein-dependent dehydrogenases (glycerol-3-phosphate dehydrogenase and succinate dehydrogenase) localized on the outer and inner face of the inner mitochondrial membrane, respectively.

AUTOTROPHIC ENZYME SYSTEMS: I. ELECTRON TRANSPORT SYSTEMS CONCERNED WITH HYDROXYLAMINE OXIDATION IN NITROSOMONAS

1963 ◽  
Vol 41 (3) ◽  
pp. 763-778 ◽  
Author(s):  
M. I. H. Aleem ◽  
H. Lees
Keyword(s):  
Electron Transport ◽  
Cytochrome C ◽  
Ammonium Ion ◽  
Transport Systems ◽  
Enzyme Complex ◽  
Reaction Sequence ◽  
Intact Cells ◽  
Cytochrome C Reductase ◽  
Enzyme Systems ◽  
Low Concentrations

Intact cells or cell-free extracts of Nitrosomonas catalyze the rapid and stoichiometric conversion of nitrohydroxylamine to nitrite at rates comparable to the oxidation of ammonium ion or hydroxylamine to nitrite. Cell-free extracts possess a powerful hydroxylamine – cytochrome c reductase activating hydroxylamine to donate electrons to the cytochrome systems comprising b, c, and a type components. The partially purified enzyme complex is sensitive to low concentrations of cyanide and inhibitors of the flavoproteins. The possible mechanism of the formation and oxidation of the new intermediate "nitrohydroxylamine" in the reaction sequence is discussed.

Mitochondrial cytochrome c oxidase and control of energy metabolism: measurements in suspensions of isolated mitochondria

2014 ◽  
Vol 117 (12) ◽  
pp. 1424-1430 ◽  
Author(s):  
David F. Wilson ◽  
David K. Harrison ◽  
Andrei Vinogradov
Keyword(s):  
Oxygen Consumption ◽  
Energy Metabolism ◽  
Cytochrome C ◽  
Oxidative Phosphorylation ◽  
Respiratory Rate ◽  
Cytochrome C Oxidase ◽  
Energy State ◽  
Atp Synthesis ◽  
Oxygen Depletion ◽  
High Energy

Cytochrome c oxidase is the enzyme responsible for oxygen consumption by mitochondrial oxidative phosphorylation and coupling site 3 of oxidative phosphorylation. In this role it determines the cellular rate of ATP synthesis by oxidative phosphorylation and is the key to understanding how energy metabolism is regulated. Four electrons are required for the reduction of oxygen to water, and these are provided by the one-electron donor, cytochrome c. The rate of oxygen consumption (ATP synthesis) is dependent on the fraction of cytochrome c reduced (fred), oxygen pressure (pO2), energy state ([ATP]/[ADP][Pi]), and pH. In coupled mitochondria (high energy state) and pO2 >60 torr, the rate increases in an exponential-like fashion with increasing fred. When the dependence on fred is fitted to the equation rate = a(fred)b, a decreased from 100 to near 20, and b increased from 1.3 to 4 as the pH of the medium increased from 6.5 to 8.3. During oxygen depletion from the medium fred progressively increases and the rate of respiration decreases. The respiratory rate falls to ½ (P50) by about 1.5 torr, at which point fred is substantially increased. The metabolically relevant dependence on pO2 is obtained by correcting for the increase in fred, in which case the P50 is 12 torr. Adding an uncoupler of oxidative phosphorylation eliminates the dependence of the cytochrome c oxidase activity on pH and energy state. The respiratory rate becomes proportional to fred and the P50 decreases to less than 1 torr.

The effect of temperature and body size on electron transport system activity in freshwater zooplankton

1978 ◽  
Vol 56 (4) ◽  
pp. 634-642 ◽  
Author(s):  
Uwe Borgmann
Keyword(s):  
Electron Transport ◽  
Cytochrome C ◽  
Organic Compounds ◽  
Transport System ◽  
Environmental Temperature ◽  
Electron Transport System ◽  
Effect Of Temperature ◽  
Unit Weight ◽  
Succinate Oxidation ◽  
Ets Activity

Electron transport system (ETS) activity in Mysis relicta, Limnocalanus macrurus, and surface zooplankton was measured by following the rate of reduction of cytochrome c in the presence of NADH, succinate, or NADPH. The steady-state kinetics indicate that NADPH is oxidized by a different ETS from NADH and succinate, and more than one system may exist for the oxidation of NADH and succinate in surface zooplankton. The NADPH requiring ETS which, because of its higher Km, presumably does not reduce cytochrome c in vivo, is probably equivalent to the microsomal NADPH requiring ETS from vertebrates and insects used in the detoxification of organic compounds. ETS activity is affected by both environmental temperature and size of the organism, with environmental temperature affecting both the total activity of the enthalpy of activation of the system. Larger organisms have a lower activity per unit weight compared with smaller animals. Because the effects of temperature and size are roughly similar for NADPH oxidation and NADH or succinate oxidation, the ratio of NADPH to either NADH or succinate oxidation may be a useful indicator of exposure to toxic organic compounds.

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