scholarly journals Pyruvate transport by thermogenic-tissue mitochondria

1987 ◽  
Vol 247 (2) ◽  
pp. 441-447 ◽  
Author(s):  
M O Proudlove ◽  
R B Beechey ◽  
A L Moore
Keyword(s):  
Alternative Oxidase ◽  
Competitive Inhibition ◽  
Feedback Inhibition ◽  
Total Activity ◽  
Mitochondrial Inner Membrane ◽  
Pyruvate Oxidation ◽  
Cytochrome Pathway ◽  
Arum Maculatum ◽  
Long Chain ◽  
Sauromatum Guttatum

1. Mitochondria isolated from the thermogenic spadices of Arum maculatum and Sauromatum guttatum plants oxidized external NADH, succinate, citrate, malate, 2-oxoglutarate and pyruvate without the need to add exogenous cofactors. 2. Oxidation of substrates was virtually all via the alternative oxidase, the cytochrome pathway constituting only 10-20% of the total activity, depending on the stage of spadix development. 3. During later stages of spadix development, pyruvate oxidation was enhanced by the addition of aspartate. This was caused by acetyl-CoA condensing with oxaloacetate, produced from pyruvate/aspartate transamination, and so decreasing feedback inhibition of pyruvate dehydrogenase. 4. Pyruvate oxidation was inhibited by the long-chain acid maleimides AM5-11, but not by those with shorter polymethylene side groups, AM1-4. 5. The alpha-cyanocinnamate derivatives UK5099 [alpha-cyano-beta-(1-phenylindol-3-yl)acrylate] and CHCA [alpha-cyano-4-hydroxycinnamate] inhibited pyruvate-dependent O2 consumption and the carrier-mediated uptake of pyruvate across the mitochondrial inner membrane. Characteristics of non-competitive inhibition were observed for CHCA, whereas for UK5099 the results were more complex, suggesting a very low rate of dissociation of the inhibitor-carrier complex. 6. A comparison of the values of Vmax. and Km for oxidation and transport suggested that it was the latter which controls the overall rate of pyruvate oxidation by mitochondria from both tissues.

scholarly journals Kinetic analysis of the mitochondrial quinol-oxidizing enzymes during development of thermogenesis in Arum maculatum L

1996 ◽  
Vol 317 (1) ◽  
pp. 313-319 ◽  
Author(s):  
Graeme R. LEACH ◽  
Klaas KRAB ◽  
David G. WHITEHOUSE ◽  
Anthony L. MOORE
Keyword(s):  
Respiratory Rate ◽  
Succinate Dehydrogenase ◽  
Oxidase Activity ◽  
Alternative Oxidase ◽  
Alternative Pathway ◽  
Respiratory Control ◽  
Stage Of Development ◽  
Activation Level ◽  
Cytochrome Pathway ◽  
Arum Maculatum

The dependence of the rate of oxygen uptake upon the ubiquinone (Q)-pool reduction level in mitochondria isolated during the development of thermogenesis of Arum maculatum spadices has been investigated. At the α-stage of development, the respiratory rate was linearly dependent upon the reduction level of the Q-pool (Qr) both under state-3 and -4 conditions. Progression through the β/γ to the Δ-stage resulted in a non-linear dependence of the state-4 rate on Qr. In the Δ-stage of development, both state-3 and -4 respiratory rates were linearly dependent upon Qr due to a shift in the engagement of the alternative oxidase to lower levels of Qr. Western blot analysis revealed that increased alternative oxidase activity could be correlated with expression of a 35 kDa protein. Respiratory control was only observed with mitochondria in the α-stage of development. At the β/γ-stage of development, the addition of ADP resulted in a significant oxidation of the Q-pool which was accompanied by a decrease in the respiratory rate. This was due either to decreased contribution of the alternative pathway to the overall respiratory rate under state 3 or by deactivation of succinate dehydrogenase activity by ADP. Cold-storage of the spadices at the β-stage of development led to increased activity of both the cytochrome pathway and succinate dehydrogenase, without any change in alternative oxidase activity. Results are discussed in terms of how changes in the activation level of the alternative oxidase and succinate dehydrogenase influence the activity and engagement of the quinol-oxidizing pathways during the development of thermogenesis in A. maculatum.

scholarly journals Characterization of cyanide-insensitive respiration in mitochondria and submitochondrial particles of Moniliella tomentosa

1979 ◽  
Vol 182 (2) ◽  
pp. 437-443 ◽  
Author(s):  
Jos Vanderleyden ◽  
Jochen Kurth ◽  
Hubert Verachtert
Keyword(s):  
Alternative Oxidase ◽  
Alternative Pathway ◽  
Total Activity ◽  
Terminal Oxidase ◽  
Submitochondrial Particles ◽  
Terminal Electron Acceptor ◽  
Cytochrome Pathway ◽  
O2 Concentration ◽  
System 2

Mitochondria and submitochondrial particles of the osmophilic yeast-like fungus Moniliella tomentosa may respire by means of two pathways: a normal cytochrome pathway, sensitive to cyanide and antimycin A, and an alternative pathway, which is insensitive to these inhibitors but is specifically inhibited by salicylhydroxamic acid. The affinities of both oxidases for succinate and NADH as substrates, for O2 as terminal electron acceptor, and for AMP as stimulator of the alternative oxidase were determined. 1. Submitochondrial particles of M. tomentosa may also respire by means of a cyanide-sensitive and/or cyanide-insensitive system. 2. The activities of both oxidases as compared with the total activity are roughly the same in submitochondrial particles as in the original mitochondria. 3. The terminal oxidase of the cyanide-insensitive pathway requires a 10-fold higher O2 concentration for saturation than does cytochrome c oxidase. 4. The apparent Km for succinate is about 3 times higher for the alternative than for the normal oxidase when measured in mitochondria, and 4–10 times higher when measured in submitochondrial particles. The apparent Km for NADH is roughly the same for both oxidases. 5. The apparent Km values of both oxidases for succinate are always lower in submitochondrial particles than in mitochondria. 6. The apparent Km for AMP, acting as a stimulator of the alternative oxidase, is the same (25μm) in mitochondria as in sub-mitochondrial particles. These results are discussed in the light of the structure and localization of the components of the alternative oxidase.

scholarly journals The tardigrade Hypsibius exemplaris  has the active mitochondrial alternative oxidase that could be studied at animal organismal level

PLoS ONE ◽  
2021 ◽  
Vol 16 (8) ◽  
pp. e0244260
Author(s):  
Daria Wojciechowska ◽  
Milena Roszkowska ◽  
Łukasz Kaczmarek ◽  
Wiesława Jarmuszkiewicz ◽  
Andonis Karachitos ◽  
...  
Keyword(s):  
Animal Model ◽  
Membrane Potential ◽  
Therapeutic Strategy ◽  
Alternative Oxidase ◽  
Mitochondrial Respiratory Chain ◽  
Whole Body ◽  
Mitochondrial Inner Membrane ◽  
Behavior Observation ◽  
Cytochrome Pathway ◽  
The Impact

Mitochondrial alternative oxidase (AOX) is predicted to be present in mitochondria of several invertebrate taxa including tardigrades. Independently of the reason concerning the enzyme occurrence in animal mitochondria, expression of AOX in human mitochondria is regarded as a potential therapeutic strategy. Till now, relevant data were obtained due to heterologous AOX expression in cells and animals without natively expressed AOX. Application of animals natively expressing AOX could importantly contribute to the research. Thus, we decided to investigate AOX activity in intact specimens of the tardigrade Hypsibius exemplaris. We observed that H. exemplaris specimens’ tolerance to the blockage of the mitochondrial respiratory chain (MRC) cytochrome pathway was diminished in the presence of AOX inhibitor and the inhibitor-sensitive respiration enabled the tardigrade respiration under condition of the blockage. Importantly, these observations correlated with relevant changes of the mitochondrial inner membrane potential (Δψ) detected in intact animals. Moreover, detection of AOX at protein level required the MRC cytochrome pathway blockage. Overall, we demonstrated that AOX activity in tardigrades can be monitored by the animals’ behavior observation as well as by measurement of intact specimens’ whole-body respiration and Δψ. Furthermore, it is also possible to check the impact of the MRC cytochrome pathway blockage on AOX level as well as AOX inhibition in the absence of the blockage on animal functioning. Thus, H. exemplaris could be consider as a whole-animal model suitable to study AOX.

Cloning and Analysis of the Alternative Oxidase Gene of Neurospora crassa

Genetics ◽  
1996 ◽  
Vol 142 (1) ◽  
pp. 129-140 ◽  
Author(s):  
Qiuhong Li ◽  
R Gary Ritzel ◽  
Lesley L T McLean ◽  
Lee McIntosh ◽  
Tak Ko ◽  
...  
Keyword(s):  
Neurospora Crassa ◽  
Alternative Oxidase ◽  
Electron Flow ◽  
Mitochondrial Protein ◽  
Transcriptional Level ◽  
Wild Type ◽  
Respiratory Pathway ◽  
Oxidase Gene ◽  
Alternative Respiratory Pathway ◽  
Cytochrome Pathway

Mitochondria of Neurospora crassa contain a cyanide-resistant alternative respiratory pathway in addition to the cytochrome pathway. The alternative oxidase is present only when electron flow through the cytochrome chain is restricted. Both genomic and cDNA copies for the alternative oxidase gene have been isolated and analyzed. The sequence of the predicted protein is homologous to that of other species. The mRNA for the alternative oxidase is scarce in wild-type cultures grown under normal conditions, but it is abundant in cultures grown in the presence of chloramphenicol, an inhibitor of mitochondrial protein synthesis, or in mutants deficient in mitochondrial cytochromes. Thus, induction of alternative oxidase appears to be at the transcriptional level. Restriction fragment length polymorphism mapping of the isolated gene demonstrated that it is located in a position corresponding to the aod-1 locus. Sequence analysis of mutant aod-1 alleles reveals mutations affecting the coding sequence of the alternative oxidase. The level of aod-1 mRNA in an aod-2 mutant strain that had been grown in the presence of chloramphenicol was reduced several fold relative to wild-type, supporting the hypothesis that the product of aod-2 is required for optimal expression of aod-1.

Alternative oxidase is an important player in the regulation of nitric oxide levels under normoxic and hypoxic conditions in plants

2019 ◽  
Vol 70 (17) ◽  
pp. 4345-4354 ◽  
Author(s):  
Aprajita Kumari ◽  
Pradeep Kumar Pathak ◽  
Mallesham Bulle ◽  
Abir U Igamberdiev ◽  
Kapuganti Jagadis Gupta
Keyword(s):  
Nitric Oxide ◽  
Alternative Oxidase ◽  
Plant Mitochondria ◽  
No Production ◽  
Complex Iv ◽  
Increase Energy Efficiency ◽  
Hypoxic Conditions ◽  
Cytochrome Pathway ◽  
Important Player ◽  
Elicitor Treatments

Abstract Plant mitochondria possess two different pathways for electron transport from ubiquinol: the cytochrome pathway and the alternative oxidase (AOX) pathway. The AOX pathway plays an important role in stress tolerance and is induced by various metabolites and signals. Previously, several lines of evidence indicated that the AOX pathway prevents overproduction of superoxide and other reactive oxygen species. More recent evidence suggests that AOX also plays a role in regulation of nitric oxide (NO) production and signalling. The AOX pathway is induced under low phosphate, hypoxia, pathogen infections, and elicitor treatments. The induction of AOX under aerobic conditions in response to various stresses can reduce electron transfer through complexes III and IV and thus prevents the leakage of electrons to nitrite and the subsequent accumulation of NO. Excess NO under various stresses can inhibit complex IV; thus, the AOX pathway minimizes nitrite-dependent NO synthesis that would arise from enhanced electron leakage in the cytochrome pathway. By preventing NO generation, AOX can reduce peroxynitrite formation and tyrosine nitration. In contrast to its function under normoxia, AOX has a specific role under hypoxia, where AOX can facilitate nitrite-dependent NO production. This reaction drives the phytoglobin–NO cycle to increase energy efficiency under hypoxia.

scholarly journals Immunological identification of the alternative oxidase of Neurospora crassa mitochondria.

1989 ◽  
Vol 9 (3) ◽  
pp. 1362-1364 ◽  
Author(s):  
A M Lambowitz ◽  
J R Sabourin ◽  
H Bertrand ◽  
R Nickels ◽  
L McIntosh
Keyword(s):  
Neurospora Crassa ◽  
Oxidase Activity ◽  
Hydroxamic Acid ◽  
Alternative Oxidase ◽  
Fungal Species ◽  
The Other ◽  
Wild Type ◽  
Higher Plant ◽  
Sauromatum Guttatum ◽  
Immunological Identification

Neurospora crassa mitochondria use a branched electron transport system in which one branch is a conventional cytochrome system and the other is an alternative cyanide-resistant, hydroxamic acid-sensitive oxidase that is induced when the cytochrome system is impaired. We used a monoclonal antibody to the alternative oxidase of the higher plant Sauromatum guttatum to identify a similar set of related polypeptides (Mr, 36,500 and 37,000) that was associated with the alternative oxidase activity of N. crassa mitochondria. These polypeptides were not present constitutively in the mitochondria of a wild-type N. crassa strain, but were produced in high amounts under conditions that induced alternative oxidase activity. Under the same conditions, mutants in the aod-1 gene, with one exception, produced apparently inactive alternative oxidase polypeptides, whereas mutants in the aod-2 gene failed to produce these polypeptides. The latter findings support the hypothesis that aod-1 is a structural gene for the alternative oxidase and that the aod-2 gene encodes a component that is required for induction of alternative oxidase activity. Finally, our results indicate that the alternative oxidase is highly conserved, even between plant and fungal species.

Functional analysis reveals effects of tobacco alternative oxidase gene (NtAOX1a) on regulation of defence responses against abiotic and biotic stresses

2009 ◽  
Vol 29 (6) ◽  
pp. 375-383 ◽  
Author(s):  
Yi Zhang ◽  
Dongmei Xi ◽  
Jian Wang ◽  
Dongfang Zhu ◽  
Xingqi Guo
Keyword(s):  
Oxidative Stress ◽  
Low Temperature ◽  
Alternative Oxidase ◽  
Alternative Pathway ◽  
Respiratory Pathway ◽  
Oxidase Gene ◽  
Biotic Stresses ◽  
Alternative Respiratory Pathway ◽  
Cytochrome Pathway ◽  
Defence Responses

Mitochondrial AOX (alternative oxidase) is the terminal oxidase of the CN (cyanide)-resistant alternative respiratory pathway in plants. To investigate the role of the tobacco AOX gene (NtAOX1a) (where Nt is Nicotiana tabacum) under deleterious conditions which could induce ROS (reactive oxygen species) accumulation, we generated and characterized a number of independent transgenic tobacco (N. tabacum) lines with altered NtAOX1a gene expression and AP (alternative pathway) capacity. AOX efficiently inhibited the production of low-temperature-induced H2O2 and might be a major enzyme for scavenging H2O2 at low temperature. Furthermore, NtAOX1a may act as a regulator of KCN-induced resistance to TMV (tobacco mosaic virus) through the regulation of H2O2. Notably, a moderate accumulation of H2O2 under the control of NtAOX1a was crucial in viral resistance. Analysis of seed germination indicated an important role for NtAOX1a in germination under H2O2-induced oxidative stress when the CP (cytochrome pathway) was inhibited. These results demonstrate that NtAOX1a is necessary for plants to survive low temperature, pathogen attack and oxidative stress by scavenging ROS under these adverse conditions when the CP is restricted.

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