scholarly journals Hydrogen peroxide production in uncoupled mitochondria of the parasitic nematode worm Nippostrongylus brasiliensis

1987 ◽  
Vol 243 (2) ◽  
pp. 589-595 ◽  
Author(s):  
T A Paget ◽  
M Fry ◽  
D Lloyd
Keyword(s):  
Electron Transport ◽  
Parasitic Nematode ◽  
H2o2 Production ◽  
Nippostrongylus Brasiliensis ◽  
Antimycin A ◽  
Transport Pathway ◽  
Salicylhydroxamic Acid ◽  
Low Concentrations ◽  
Carbonyl Cyanide ◽  
Nematode Worm

1. Mitochondria from the parasitic nematode worm Nippostrongylus brasiliensis produce H2O2 in the energized state; higher rates of H2O2 production were observed in the presence of the uncoupler carbonyl cyanide m-chlorophenylhydrazone. 2. Antimycin A inhibits respiration and H2O2 production by 70 and 65% respectively; the residual activities can be attributed to alternative electron-transport pathway(s). 3. o-Hydroxydiphenyl and 1,3,5-trihydroxybenzene, inhibitors of alternative electron transport, inhibit respiration by 37% and H2O2 production by 26%. 4. Another inhibitor of alternative electron transport, salicylhydroxamic acid, shows a complex mode of action; low concentrations (less than 0.5 mM) stimulate respiration and H2O2 production, whereas 2 mM-salicylhydroxamic acid inhibited respiration by 35% and stopped H2O2 production completely. 5. O2 thresholds were observed for the inhibition of respiration at O2 concentrations greater than 57.7 microM and inhibition of H2O2 production (greater than 20.5 microM-O2); apparent Km values for oxygen were 5.5 microM and 3.0 microM respectively. 6. In the presence of antimycin A the O2-inhibition thresholds and apparent Km values for O2 of respiration and H2O2 production matched closely, suggesting that the alternative oxidase is a likely site of H2O2 production. 7. These results are discussed in relation to O2 toxicity to N. brasiliensis.

scholarly journals The O2-dependence of respiration and H2O2 production in the parasitic nematode Ascaridia galli

1988 ◽  
Vol 256 (2) ◽  
pp. 633-639 ◽  
Author(s):  
T A Paget ◽  
M Fry ◽  
D Lloyd
Keyword(s):  
Electron Transport ◽  
Muscle Tissue ◽  
Parasitic Nematode ◽  
H2o2 Production ◽  
Reproductive Tissue ◽  
Ascaridia Galli ◽  
Transport Pathway ◽  
Transport Pathways ◽  
Transport Chain ◽  
Carbonyl Cyanide

1. Respiration in the parasitic nematode worm Ascaridia galli was inhibited at O2 concentrations in excess of 255 microM, and an apparent Km,O2 of 174 microM was determined. 2. Mitochondria-enriched fractions isolated from the tissues of A. galli have much lower apparent Km,O2 values (approx. 5 microM). They produce H2O2 in the energized state; higher rates of H2O2 production were observed in the presence of the uncoupler carbonyl cyanide m-chlorophenylhydrazone. 3. Antimycin A inhibited respiration in muscle tissue mitochondria by 10%, but had no effect on respiration in gut + reproductive tissue mitochondria; the major portion of respiration in both types of mitochondria could be attributed to an alternative electron-transport pathway. 4. o-Hydroxydiphenyl, an inhibitor of alternative electron-transport pathways, inhibits respiration by 98% and completely inhibits the production of H2O2 in gut-plus-reproductive-tissue mitochondria; respiration and H2O2 production in muscle tissue mitochondria were inhibited by 90 and 86% respectively. 5. Another inhibitor of alternative electron transport, salicylhydroxamic acid, had the same effect as o-hydroxydiphenyl on H2O2 production and respiration in gut-plus-reproductive-tissue mitochondria. However, its effect on muscle tissue mitochondria was complex; a low concentration (0.35 mM) stimulated H2O2 production, whereas 3 mM inhibited respiration by 87% and prevented H2O2 production completely. 6. The similarities between the apparent Km,O2 values for H2O2 production and respiration in muscle mitochondria and in gut-plus-reproductive-tissue mitochondria suggests that the site of H2O2 production on the alternative electron-transport chain is cytochrome ‘o’. 7. These results are discussed in relation to potential O2 toxicity in A. galli.

scholarly journals Properties of mitochondria isolated from cyanide-sensitive and cyanide-stimulated cultures of Acanthamoeba castellanii

1978 ◽  
Vol 174 (1) ◽  
pp. 203-211 ◽  
Author(s):  
Steven W. Edwards ◽  
David Lloyd
Keyword(s):  
Electron Transport ◽  
Respiratory Control ◽  
Acanthamoeba Castellanii ◽  
Type A ◽  
Antimycin A ◽  
Type B ◽  
Transport Pathway ◽  
Salicylhydroxamic Acid ◽  
Stages Of Growth ◽  
Electron Transport Pathway

1. Mitochondria isolated from cultures of Acanthamoeba castellanii exhibit respiratory control and oxidize α-oxoglutarate, succinate and NADH with ADP:O ratios of about 2.4, 1.4 and 1.25 respectively. 2. Mitochondria from cultures of which the respiration was stimulated up to 50% by 1mm-cyanide (type-A mitochondria) and from cyanide-sensitive cultures (type-B mitochondria) had similar respiratory-control ratios and ADP:O ratios. 3. State-3 rates of respiration were generally more cyanide-sensitive than State-4 rates, and the respiration of type-A mitochondria was more cyanide-resistant than that of type-B mitochondria. 4. Salicylhydroxamic acid alone had little effect on respiratory activities of either type of mitochondria, but when added together with cyanide, irrespective of the order of addition, inhibition was almost complete. 5. Oxidation of externally added NADH by type-A mitochondria was mainly via an oxidase with a low affinity for oxygen (Km[unk]15μm), which was largely cyanide-sensitive and partially antimycin A-sensitive; this electron-transport pathway was inhibited by ADP. 6. Cyanide-insensitive but salicylhydroxamic acid-sensitive respiration was stimulated by AMP and ADP, and by ATP after incubation in the presence of MgCl2. 7. Addition of rotenone to mitochondria oxidizing α-oxoglutarate lowered the ADP:O ratios by about one-third and rendered inhibition by cyanide more complete. 8. The results suggest that mitochondria of A. castellanii possess branched pathways of electron transport which terminate in three separate oxidases; the proportions of electron fluxes via these pathways vary at different stages of growth.

scholarly journals Cyanide-insensitive oxidation of ascorbate + NNN′N′-tetramethyl-p-phenylenediamine mixture by mung-bean (Phaseolus aureus) mitochondria. An energy-linked function

1978 ◽  
Vol 176 (1) ◽  
pp. 129-136 ◽  
Author(s):  
S B Wilson
Keyword(s):  
Oxygen Uptake ◽  
Mung Bean ◽  
Electron Flow ◽  
Plant Mitochondria ◽  
Phosphorylation Site ◽  
Antimycin A ◽  
Phaseolus Aureus ◽  
Salicylhydroxamic Acid ◽  
Low Concentrations ◽  
High Concentrations

Freshly prepared washed or purified mung-bean (Phaseolus aureus) mitochondria utilize oxygen with ascorbate/tetramethyl-p-phenylenediamine mixture as electron donor in the presence of KCN. ATP control of the oxygen uptake can be observed with very fresh mitochondria. The electron flow, which is inhibited by antimycin A, salicylhydroxamic acid or octylguanidine, takes place by reversed electron transport through phosphorylation site II and thence to oxygen through the cyanide-insensitive pathway. Oligomycin and low concentrations of uncoupler partially inhibit the oxygen uptake in a manner similar to that observed for other energy-linked functions of plant mitochondria. An antimycin A-insensitive oxygen uptake occurs if high concentrations of uncoupler are used, indicating that the pathway of electron flow has been altered. The process of cyanide-insensitive ascorbate oxidation is self-starting, and, since it occurs in the presence of oligomycin, it is concluded that the reaction can be energized by a single energy-conservation site associated with the cyanide-insensitive oxidase pathway.

Effects of electron transport inhibitors and uncouplers on the oxidation of ferrous iron and compounds interacting with ferric iron inAcidithiobacillus ferrooxidans

2005 ◽  
Vol 51 (8) ◽  
pp. 695-703 ◽  
Author(s):  
Yongqiang Chen ◽  
Isamu Suzuki
Keyword(s):  
Electron Transport ◽  
Cytochrome Oxidase ◽  
Complex I ◽  
Ferric Iron ◽  
Complex Iii ◽  
Transport Pathway ◽  
Low Concentrations ◽  
Transport Inhibitors ◽  
A Site ◽  
Electron Transport Pathway

Oxidation of Fe2+, ascorbic acid, propyl gallate, tiron, L-cysteine, and glutathione by Acidithiobacillus ferrooxidans was studied with respect to the effect of electron transport inhibitors and uncouplers on the rate of oxidation. All the oxidations were sensitive to inhibitors of cytochrome c oxidase, KCN, and NaN3. They were also partially inhibited by inhibitors of complex I and complex III of the electron transport system. Uncouplers at low concentrations stimulated the oxidation and inhibited it at higher concentrations. The oxidation rates of Fe2+and L-cysteine inhibited by complex I and complex III inhibitors (amytal, rotenone, antimycin A, myxothiazol, and HQNO) were stimulated more extensively by uncouplers than the control rates. Atabrine, a flavin antagonist, was an exception, and atabrine-inhibited oxidation activities of all these compounds were further inhibited by uncouplers. A model for the electron transport pathways of A. ferrooxidans is proposed to account for these results. In the model these organic substrates reduce ferric iron on the surface of cells to ferrous iron, which is oxidized back to ferric iron through the Fe2+oxidation pathway, leading to cytochrome oxidase to O2. Some of electrons enter the uphill (energy-requiring) electron transport pathway to reduce NAD+. Uncouplers at low concentrations stimulate Fe2+oxidation by stimulating cytochrome oxidase by uncoupling. Higher concentrations lower Δp to the level insufficient to overcome the potentially uphill reaction at rusticyanin-cytochrome c4. Inhibition of uphill reactions at complex I and complex III leads to Δp accumulation and inhibition of cytochrome oxidase. Uncouplers remove the inhibition of Δp and stimulate the oxidation. Atabrine inhibition is not released by uncouplers, which implies a possibility of atabrine inhibition at a site other than complex I, but a site somehow involved in the Fe2+oxidation pathway.Key words: Acidithiobacillus ferrooxidans, electron transport, uncouplers, uphill electron transport pathway.

scholarly journals Inhibition and uncoupling of photophosphorylation in isolated chloroplasts by organotin, organomercury and diphenyleneiodonium compounds

1974 ◽  
Vol 142 (1) ◽  
pp. 65-74 ◽  
Author(s):  
Angela S. Watling-Payne ◽  
Michael J. Selwyn
Keyword(s):  
Electron Transport ◽  
Organotin Compounds ◽  
O2 Evolution ◽  
Phenylmercuric Acetate ◽  
Low Concentrations ◽  
Hydrophobic Site ◽  
Carbonyl Cyanide ◽  
High Concentrations ◽  
Highly Hydrophobic ◽  
Isolated Chloroplasts

1. Trialkyltin, triphenyltin and diphenyleneiodonium compounds inhibited ADP-stimulated O2 evolution by isolated pea chloroplasts in the presence of phosphate or arsenate. Tributyltin and triphenyltin were the most effective inhibitors, which suggests a highly hydrophobic site of action. Phenylmercuric acetate was a poor inhibitor of photophosphorylation, which suggests that thiol groups are not involved. 2. Triethyltin was a potent uncoupler of photophosphorylation by isolated chloroplasts in media containing Cl-, but had little uncoupling activity when Cl- was replaced by NO3- or SO42-, which are inactive in the anion–hydroxide exchange. It is suggested that uncoupling by triethyltin is a result of the Cl-–OH- exchange together with a natural uniport of Cl-. Tributyltin, triphenyltin and phenylmercuric acetate had low uncoupling activity, probably because in these compounds the uncoupling activity is partially masked by inhibitory effects. 3. At high concentrations the organotin compounds caused inhibition of electron transport uncoupled by carbonyl cyanide m-chlorophenylhydrazone or NH4Cl. At these high concentrations the organotin compounds may be producing a detergent-like disorganization of the membrane structure. In contrast, diphenyleneiodonium sulphate inhibited uncoupled electron transport at low concentrations; however, this inhibition is less than the inhibition of photophosphorylation, which suggests that the compound also inhibits the phosphorylation reactions as well as electron transport. 4. The effects of these compounds on basal electron transport were complex and depended on the pH of the reaction media. However, they can be explained on the basis of three actions: inhibition of the phosphorylation reactions, uncoupling and direct inhibition of electron transport. 5. The inhibition of cyclic photophosphorylation in the presence of phenazine methosulphate by diphenyleneiodonium sulphate shows that it inhibits in the region of photosystem 1.

Proton motive force in a photodenitrifier, Rhodopseudomonas sphaeroides forma specialis denitrificans

1986 ◽  
Vol 64 (4) ◽  
pp. 328-336
Author(s):  
Balaram Kundu ◽  
D. J. D. Nicholas
Keyword(s):  
Electron Transport ◽  
Dark Respiration ◽  
Photosynthetic Electron Transport ◽  
Proton Motive Force ◽  
Motive Force ◽  
Antimycin A ◽  
Rhodopseudomonas Sphaeroides ◽  
Ph Values ◽  
Carbonyl Cyanide ◽  
Light Inhibition

The washed cells of Rhodopseudomonas sphaeroides f.sp. denitrificans developed a Δp of about −175 to −200 mV during denitrification in the dark and −200 to −245 mV in the light. With NO2− as the terminal acceptor, Δp was less than with NO3−, N2O, or O2. The values of Δψ in the dark were about −150 mV for NO3− and N2O and −140 mV for NO2−. During photodenitrification with NO3−, NO2−, or N2O or respiration to O2 in light, Δψ ranged between −152 and −167 mV. Like Δψ, the ΔpH was higher in light than in the dark, resulting in a 20- to 30-mV increase in Δp during illumination with NO3−, NO2−, or N2O as the acceptor. Both ΔpH and Δψ were reduced at higher pH values (≥ 7.5). Changes in pH in response to O2 in the light were less than those in the dark, indicating light inhibition of O2 respiration. The cells maintained a reasonably high Δp without addition of a substrate or when inhibitors were used; the cells retained a fairly high Δψ even in the presence of an inhibitor. However, ΔpH was appreciably lowered and in some cases it was almost abolished when either KCN, rotenone, NaN3, carbonyl cyanide m-chlorophenylhydrazone (CCCP), 2,4-dinitrophenol, N,N′-dicyclohexylcarbodiimide, antimycin A, or 2-n-heptyl-4-hydroxyquinoline-N-oxide (HOQNO) was used. The combination of an uncoupler (e.g., CCCP) and an electron transport effector (e.g., antimycin A) further reduced the ΔpH. Antimycin A and HOQNO were more effective in inhibiting photosynthetic electron transport to NO3−, NO2−, N2O, or O2 than the dark respiration to these substrates. Dibromomethylisopropyl-p-benzoquinone, a quinone antagonist, markedly reduced ΔpH in light with NO3−, NO2−, N2O, or O2 as the terminal acceptor, indicating that photosynthetically generated electrons are used for denitrification in this bacterium.

scholarly journals Electrical characteristics of amyloid beta peptides in vertical junctions

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Sohyeon Seo ◽  
Jinju Lee ◽  
Jungsue Choi ◽  
G. Hwan Park ◽  
Yeseul Hong ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Electron Transport ◽  
Amyloid Beta ◽  
Field Effect Transistors ◽  
Brain Diseases ◽  
Electrical Characteristics ◽  
Transport Pathway ◽  
Sequence Dependence ◽  
Aβ Oligomers ◽  
Aβ Peptides

AbstractAssembled amyloid beta (Aβ) peptides have been considered pathological assemblies involved in human brain diseases, and the electron transfer or electron transport characteristics of Aβ are important for the formation of structured assemblies. Here, we report the electrical characteristics of surface-assembled Aβ peptides similar to those observed in Alzheimer’s patients. These characteristics correlate to their electron transfer characteristics. Electrical current–voltage plots of Aβ vertical junction devices show the Aβ sequence dependence of the current densities at both Aβ monomers (mono-Aβs) and Aβ oligomers (oli-Aβs), while Aβ sequence dependence is not clearly observed in the electrical characteristics of Aβ planar field effect transistors (FETs). In particular, surface oligomerization of Aβ peptides drastically decreases the activity of electron transfer, which presents a change in the electron transport pathway in the Aβ vertical junctions. Electron transport at oli-Aβ junctions is symmetric (tunneling/tunneling) due to the weak and voltage-independent coupling of the less redox-reactive oli-Aβ to the contacts, while that at mono-Aβ junctions is asymmetric (hopping/tunneling) due to redox levels of mono-Aβ voltage-dependently coupled with contact electrodes. Consequently, through vertical junctions, the sequence- and conformation-dependent electrical characteristics of Aβs can reveal their electron transfer activities.

scholarly journals A Single Amino Acid Alteration in PGR5 Confers Resistance to Antimycin A in Cyclic Electron Transport around PSI

2013 ◽  
Vol 54 (9) ◽  
pp. 1525-1534 ◽  
Author(s):  
Kazuhiko Sugimoto ◽  
Yuki Okegawa ◽  
Akihiko Tohri ◽  
Terri A. Long ◽  
Sarah F. Covert ◽  
...  
Keyword(s):  
Amino Acid ◽  
Electron Transport ◽  
Single Amino Acid ◽  
Antimycin A ◽  
Cyclic Electron Transport ◽  
Acid Alteration ◽  
Amino Acid Alteration
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