Alternative oxidase in the branched mitochondrial respiratory network: an overview on structure, function, regulation, and role

Sluse, Francis; Jarmuszkiewicz, Wiesława

doi:10.1590/s0100-879x1998000600003

Cited by 77 publications

(48 citation statements)

References 81 publications

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“…The ADP/O method is valid if several requirements are fulfilled as described in Ref. 1. In order to describe how the contribution of each pathway changes with variation of state 3 respiratory rate, n-butyl malonate, a non-penetrating competitive inhibitor of succinate uptake, was used to decrease succinate availability and the rate of the quinone-reducing step (see Figure 2).…”

Section: True Contributions Of Aox Pump and Atp Synthesis To State 3mentioning

confidence: 99%

Activity and functional interaction of alternative oxidase and uncoupling protein in mitochondria from tomato fruit

Sluse

Jarmuszkiewicz

2000

Braz J Med Biol Res

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Cyanide-resistant alternative oxidase (AOX) is not limited to plant mitochondria and is widespread among several types of protists. The uncoupling protein (UCP) is much more widespread than previously believed, not only in tissues of higher animals but also in plants and in an amoeboid protozoan. The redox energy-dissipating pathway (AOX) and the proton electrochemical gradient energy-dissipating pathway (UCP) lead to the same final effect, i.e., a decrease in ATP synthesis and an increase in heat production. Studies with green tomato fruit mitochondria show that both proteins are present simultaneously in the membrane. This raises the question of a specific physiological role for each energy-dissipating system and of a possible functional connection between them (shared regulation). Linoleic acid, an abundant free fatty acid in plants which activates UCP, strongly inhibits cyanide-resistant respiration mediated by AOX. Moreover, studies of the evolution of AOX and UCP protein expression and of their activities during post-harvest ripening of tomato fruit show that AOX and plant UCP work sequentially: AOX activity decreases in early post-growing stages and UCP activity is decreased in late ripening stages. Electron partitioning between the alternative oxidase and the cytochrome pathway as well as H + gradient partitioning between ATP synthase and UCP can be evaluated by the ADP/O method. This method facilitates description of the kinetics of energy-dissipating pathways and of ATP synthase when state 3 respiration is decreased by limitation of oxidizable substrate.

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Section: True Contributions Of Aox Pump and Atp Synthesis To State 3mentioning

confidence: 99%

Activity and functional interaction of alternative oxidase and uncoupling protein in mitochondria from tomato fruit

Sluse

Jarmuszkiewicz

2000

Braz J Med Biol Res

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“…In addition to the alternative oxidase (AOX) [1][2][3], some plant mitochondria contain another energy-dissipating system, namely a plant uncoupling mitochondrial protein (PUMP) [4,5]. The cyanide (CN)-and antimycin-resistant AOX, which bypasses the main cytochrome respiratory chain, catalyzes ubiquinol-oxygen oxido-reduction without H + release in the cytosol and thus dissipates redox potential energy [1 3].…”

Section: Introductionmentioning

confidence: 99%

“…a decrease in oxidative phosphorylation efficiency), they may have different physiological functions in plant cells. While activities of both proteins can counteract the imbalances between the supply of reducing substrates and the energy and carbon demand for biosynthesis [1,3,5], only PUMP can totally switch off chemiosmotic coupling. A puzzling question regarding the presence of these two energy-dissipating systems relates to a possible connection between their activities (shared regulation).…”

Section: Introductionmentioning

confidence: 99%

Free fatty acids regulate the uncoupling protein and alternative oxidase activities in plant mitochondria

et al. 1998

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Two energy-dissipating systems, an alternative oxidase and an uncoupling protein, are known to exist in plant mitochondria. In tomato fruit mitochondria linoleic acid, a substrate for the uncoupling protein, inhibited the alternative oxidase-sustained respiration and decreased the ADPIO ratio to the same value regardless of the level of alternative oxidase activity. Experiments with varying concentrations of linoleic acid have shown that inhibition of the alternative oxidase is more sensitive to the linoleic acid concentration than the uncoupling protein activation. It can be proposed that these dissipating systems work sequentially during the life of the plant cell, since a high level of free fatty acid-induced uncoupling protein activity excludes alternative oxidase activity.

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“…Electron transport through the AOX pathway occurs without proton translocation and, consequently, is not coupled to ATP synthesis or energy conservation (for review, see Millar et al, 2011). In this case, most of the energy is dissipated as heat (Sluse and Jarmuszkiewicz, 1998;Affourtit et al, 2002). The dimeric AOX mediates the terminal step of the alternative pathway and is localized to the inner mitochondrial membrane, with its catalytic centers oriented toward the matrix (Juszczuk and Rychter, 2003).…”

mentioning

confidence: 99%

Alternative Oxidase Isoforms Are Differentially Activated by Tricarboxylic Acid Cycle Intermediates

et al. 2017

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The cyanide-insensitive alternative oxidase (AOX) is a non-proton-pumping ubiquinol oxidase that catalyzes the reduction of oxygen to water and is posttranslationally regulated by redox mechanisms and 2-oxo acids. Arabidopsis (Arabidopsis thaliana) possesses five AOX isoforms (AOX1A-AOX1D and AOX2). AOX1D expression is increased in aox1a knockout mutants from Arabidopsis (especially after restriction of the cytochrome c pathway) but cannot compensate for the lack of AOX1A, suggesting a difference in the regulation of these isoforms. Therefore, we analyzed the different AOX isoenzymes with the aim to identify differences in their posttranslational regulation. Seven tricarboxylic acid cycle intermediates (citrate, isocitrate, 2-oxoglutarate, succinate, fumarate, malate, and oxaloacetate) were tested for their influence on AOX1A, AOX1C, and AOX1D wild-type protein activity using a refined in vitro system. AOX1C is insensitive to all seven organic acids, AOX1A and AOX1D are both activated by 2-oxoglutarate, but only AOX1A is additionally activated by oxaloacetate. Furthermore, AOX isoforms cannot be transformed to mimic one another by substituting the variable cysteine residues at position III in the protein. In summary, we show that AOX isoforms from Arabidopsis are differentially fine-regulated by tricarboxylic acid cycle metabolites (most likely depending on the amino-terminal region around the highly conserved cysteine residues known to be involved in regulation by the 2-oxo acids pyruvate and glyoxylate) and propose that this is the main reason why they cannot functionally compensate for each other.

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Alternative oxidase in the branched mitochondrial respiratory network: an overview on structure, function, regulation, and role

Cited by 77 publications

References 81 publications

Activity and functional interaction of alternative oxidase and uncoupling protein in mitochondria from tomato fruit

Activity and functional interaction of alternative oxidase and uncoupling protein in mitochondria from tomato fruit

Free fatty acids regulate the uncoupling protein and alternative oxidase activities in plant mitochondria

Alternative Oxidase Isoforms Are Differentially Activated by Tricarboxylic Acid Cycle Intermediates

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