Activity of the mitochondrial pyruvate dehydrogenase complex in plants is stimulated in the presence of malate

Igamberdiev, Abir U.; Lernmark, Ulrikа; Gardeström, Per

doi:10.1016/j.mito.2014.04.006

Cited by 28 publications

(17 citation statements)

References 55 publications

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“…The activation of PEPC in the induced TPS29.2 plants stimulates flux of 13 C into malate and fumarate. If malate is transported into the mitochondria, it may be decarboxylated to pyruvate by NAD + ‐malic enzyme (NAD–ME), providing an alternative source of substrate for mPDH and potentially stimulating mPDH activity by inhibiting mPDH protein kinase (Igamberdiev et al ., ). Entry of fumarate into the mitochondria may promote this cascade by relieving inhibition of the NAD–ME by malate (Tronconi et al ., ).…”

Section: Discussionmentioning

confidence: 97%

Trehalose 6–phosphate coordinates organic and amino acid metabolism with carbon availability

et al. 2016

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SUMMARYTrehalose 6-phosphate (Tre6P) is an essential signal metabolite in plants, linking growth and development to carbon metabolism. The sucrose-Tre6P nexus model postulates that Tre6P acts as both a signal and negative feedback regulator of sucrose levels. To test this model, short-term metabolic responses to induced increases in Tre6P levels were investigated in Arabidopsis thaliana plants expressing the Escherichia coli Tre6P synthase gene (otsA) under the control of an ethanol-inducible promoter. Increased Tre6P levels led to a transient decrease in sucrose content, post-translational activation of nitrate reductase and phosphoenolpyruvate carboxylase, and increased levels of organic and amino acids. Radio-isotope ( 14 CO 2 ) and stable isotope ( 13 CO 2 ) labelling experiments showed no change in the rates of photoassimilate export in plants with elevated Tre6P, but increased labelling of organic acids. We conclude that high Tre6P levels decrease sucrose levels by stimulating nitrate assimilation and anaplerotic synthesis of organic acids, thereby diverting photoassimilates away from sucrose to generate carbon skeletons and fixed nitrogen for amino acid synthesis. These results are consistent with the sucrose-Tre6P nexus model, and implicate Tre6P in coordinating carbon and nitrogen metabolism in plants.

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Section: Discussionmentioning

confidence: 97%

Trehalose 6–phosphate coordinates organic and amino acid metabolism with carbon availability

et al. 2016

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“…Redox balance is controlled by malate dehydrogenase reaction in mitochondria, which was established both on isolated organelles (Palmer et al 1982, Hagedorn et al 2004) and using transgenic plants deficient in the mitochondrial malate dehydrogenase (Tomaz et al 2010, Lindén et al 2016). This prevents a strong increase in NADH/NAD + ratio and thereby supports operation of pyruvate dehydrogenase (Igamberdiev et al 2014b) and glycine decarboxylase (Bykova et al 2014). In this way, optimized fluxes via these enzymes in the light are maintained and provide substrates for biosynthesis reactions from the TCA cycle and refixation of photorespiratory ammonium (Gardeström et al 2002).…”

Section: Intercompartmental Redox Regulation and Atp Balance In Photomentioning

confidence: 99%

The origin of cytosolic ATP in photosynthetic cells

Gardeström

Igamberdiev

2016

Physiologia Plantarum

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In photosynthetically active cells, both chloroplasts and mitochondria have the capacity to produce ATP via photophosphorylation and oxidative phosphorylation, respectively. Thus, theoretically, both organelles could provide ATP for the cytosol, but the extent, to which they actually do this, and how the process is regulated, both remain unclear. Most of the evidence discussed comes from experiments with rapid fractionation of isolated protoplasts subjected to different treatments in combination with application of specific inhibitors. The results obtained indicate that, under conditions where ATP demand for photosynthetic CO2 fixation is sufficiently high, the mitochondria supply the bulk of ATP for the cytosol. In contrast, under stress conditions where CO2 fixation is severely limited, ATP will build up in chloroplasts and it can then be exported to the cytosol, by metabolite shuttle mechanisms. Thus, depending on the conditions, either mitochondria or chloroplasts can supply the bulk of ATP for the cytosol. This supply of ATP is discussed in relation to the idea that mitochondrial functions may be tuned to provide an optimal environment for the chloroplast. By balancing cellular redox states, mitochondria can contribute to an optimal photosynthetic capacity.

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“…It has been discussed that mtNAD‐MDH could play an important role in decreasing the concentration of NADH and relieving its inhibitory effect on PDC (Igamberdiev et al . ), or mtNAD‐MDH could recycle the NADH from glycine oxidation to keep NADH concentrations low and thus prevent substrate inhibition of GDC (Bykova et al . ).…”

Section: Introductionmentioning

confidence: 99%

Malate valves: old shuttles with new perspectives

2018

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Malate valves act as powerful systems for balancing the ATP/NAD(P)H ratio required in various subcellular compartments in plant cells. As components of malate valves, isoforms of malate dehydrogenases (MDHs) and dicarboxylate translocators catalyse the reversible interconversion of malate and oxaloacetate and their transport. Depending on the co-enzyme specificity of the MDH isoforms, either NADH or NADPH can be transported indirectly. Arabidopsis thaliana possesses nine genes encoding MDH isoenzymes. Activities of NAD-dependent MDHs have been detected in mitochondria, peroxisomes, cytosol and plastids. In addition, chloroplasts possess a NADP-dependent MDH isoform. The NADP-MDH as part of the 'light malate valve' plays an important role as a poising mechanism to adjust the ATP/NADPH ratio in the stroma. Its activity is strictly regulated by post-translational redox-modification mediated via the ferredoxin-thioredoxin system and fine control via the NADP /NADP(H) ratio, thereby maintaining redox homeostasis under changing conditions. In contrast, the plastid NAD-MDH ('dark malate valve') is constitutively active and its lack leads to failure in early embryo development. While redox regulation of the main cytosolic MDH isoform has been shown, knowledge about regulation of the other two cytosolic MDHs as well as NAD-MDH isoforms from peroxisomes and mitochondria is still lacking. Knockout mutants lacking the isoforms from chloroplasts, mitochondria and peroxisomes have been characterised, but not much is known about cytosolic NAD-MDH isoforms and their role in planta. This review updates the current knowledge on MDH isoforms and the shuttle systems for intercompartmental dicarboxylate exchange, focusing on the various metabolic functions of these valves.

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Activity of the mitochondrial pyruvate dehydrogenase complex in plants is stimulated in the presence of malate

Cited by 28 publications

References 55 publications

Trehalose 6–phosphate coordinates organic and amino acid metabolism with carbon availability

Trehalose 6–phosphate coordinates organic and amino acid metabolism with carbon availability

The origin of cytosolic ATP in photosynthetic cells

Malate valves: old shuttles with new perspectives

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