Evidence for Metabolic Domains within the Matrix Compartment of Pea Leaf Mitochondria

Wiskich, Joseph T.; Bryce, James H.; Day, David A.; Dry, Ian B.

doi:10.1104/pp.93.2.611

Cited by 40 publications

(16 citation statements)

References 25 publications

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“…Binding of NADH to the glycine decarboxylase complex might decrease the amount of free NADH available to other enzymes and be one of the reasons why glycine is preferred over other mitochondrial respiratory substrates (Oliver et al, 1990;Møller, 2001). (1) The oxidation of Gly and malate by pea leaf mitochondria shows rather complex interactions, which have implications for their function in photorespiration (Wiskich et al, 1990). (2) Pea leaf mitochondria contain appreciable amounts of NADP(H), which can also vary significantly in reduction level (Agius et al, 2001;Igamberdiev and Gardeströ m, 2003).…”

Section: Discussionmentioning

confidence: 99%

The Free NADH Concentration Is Kept Constant in Plant Mitochondria under Different Metabolic Conditions

et al. 2006

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The reduced coenzyme NADH plays a central role in mitochondrial respiratory metabolism. However, reports on the amount of free NADH in mitochondria are sparse and contradictory. We first determined the emission spectrum of NADH bound to proteins using isothermal titration calorimetry combined with fluorescence spectroscopy. The NADH content of actively respiring mitochondria (from potato tubers [Solanum tuberosum cv Bintje]) in different metabolic states was then measured by spectral decomposition analysis of fluorescence emission spectra. Most of the mitochondrial NADH is bound to proteins, and the amount is low in state 3 (substrate þ ADP present) and high in state 2 (only substrate present) and state 4 (substrate þ ATP). By contrast, the amount of free NADH is low but relatively constant, even increasing a little in state 3. Using modeling, we show that these results can be explained by a 2.5-to 3-fold weaker average binding of NADH to mitochondrial protein in state 3 compared with state 4. This indicates that there is a specific mechanism for free NADH homeostasis and that the concentration of free NADH in the mitochondrial matrix per se does not play a regulatory role in mitochondrial metabolism. These findings have far-reaching consequences for the interpretation of cellular metabolism.

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Section: Discussionmentioning

confidence: 99%

The Free NADH Concentration Is Kept Constant in Plant Mitochondria under Different Metabolic Conditions

et al. 2006

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“…Wiskich et al (34) concluded that the Krebs cycle can operate simultaneously with glycine oxidation by the existence of metabolons, i.e. nonhomogeneous distribution of enzymes or regions of the mitochondria where glycine oxidation enzymes occur and other regions where only the Krebs cycle is operational.…”

Section: Discussionmentioning

confidence: 99%

Light Regulation of Leaf Mitochondrial Pyruvate Dehydrogenase Complex

Gemel¹,

Randall²

1992

Plant Physiol.

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Light-dependent inactivation of mitochondrial pyruvate dehydrogenase complex (mtPDC) in pea (Pisum sativum L.) leaves was further characterized, and this phenomenon was extended to several monocot and dicot species. The light-dependent inactivation of mtPDC in vivo was rapidly reversed in the dark, even after prolonged illumination. The mtPDC can be efficiently cycled through the inactivated-reactivated status by rapid light-dark cycling. Light-dependent inactivation of mtPDC was shown to be suppressed by inhibitors of photorespiratory carbon metabolism, including 2-pyridylhydroxymethane sulfonate, isonicotinic acid hydrazide, and aminoacetonitrile, and by an inhibitor of photosynthesis, 3-(3,4-dichlorophenyl)-1,1-dimethylurea. Glycine fed to pea leaf strips in the dark yielded partially inactivated leaf mtPDC, and this inactivation was blocked by inhibitors of glycine oxidation. It is concluded that the photorespiratory glycine to serine conversion that occurs in C3 leaf mitochondria can provide the NADH to drive oxidative phosphorylation and subsequent inactivation of mtPDC. Glycine oxidation also produces ammonium ion, which has been shown to enhance the inactivation of mtPDC in vitro by stimulating the pyruvate dehydrogenase kinase that catalyzes the phosphorylation (inactivation) of the mtPDC. Thus, light-dependent, photorespiration-stimulated inactivation of the mtPDC can regulate carbon entry into the Krebs cycle during C3 photosynthesis.The mtPDC2 links glycolytic carbon metabolism with the Krebs cycle by catalyzing the oxidative decarboxylation of pyruvate to acetyl-CoA. Pyruvate provides the primary substrate for the Krebs cycle, which, in turn, provides the reducing equivalents for ATP production by oxidative phosphorylation. for regulation of the mitochondrial complex through product feedback by NADH and acetyl-CoA (23) and inactivationreactivation by reversible phosphorylation (26,27). Plants are unique in having an additional isoform of PDC in their plastids (10, 11) that is also quite sensitive to product feedback regulation but does not undergo regulation by reversible phosphorylation (10,27). In vitro studies of the PDC kinase have also shown that the phosphorylation-inactivation reaction is stimulated by micromolar NH4+ (29) and is inhibited by pyruvate, the substrate for the PDC (26,30). In situ studies with purified pea leaf mitochondria have shown that the PDC phosphorylation status is increased when the mitochondria are oxidizing substrates other than pyruvate (6), in particular, glycine, an intermediate of the photorespiratory carbon oxidation pathway.The controversy of whether or not mitochondrial respiration is occurring during photosynthesis has been long standing (16), and recent reports by Kromer and colleagues (20, 21) working with barley (Hordeum vulgare) leaf protoplasts provide convincing evidence that mitochondrial ATP production is required for optimal photosynthesis. However, Budde and Randall (7,8) recently reported that the pea leaf mtPDC is primarily in an inactivate...

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“…It has been shown that under illumination NADH production in leaf mitochondria proceeds mainly via glycine decarboxylase, the most important reaction in this organelle (Oliver et al, 1990). NADH is reoxidized via the oxalacetate/malate shuttle system or the respiratory chain to support ATP production, which is also active during the daytime (Wiskich et al, 1990). In the light of these findings the higher levels of GDH and glutamate in family 7-33 than in 8-103 indicate a higher rate of NADH synthesis by glutamate oxidation and the concurrent lower glycine content could indicate a lower rate via glycine decarboxylation.…”

Section: Discussionmentioning

confidence: 99%

Effects of ozone on foliar nitrogen metabolism of Pinus taeda L. and implications for carbohydrate metabolism

1992

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SUMMARYDose-response relationship of ozone effects on foliar nitrogen metabolism of two half-sib families of Pinus taeda L. was studied. Trees were exposed to six ozone concentrations, ranging from 0 2 to 3 times the ambient, for two consecutive growing seasons (1988 and 1989) in open-top chambers. Content of total chlorophyll, soluble protein and soluble amino acids, and activities of glutamine synthetase and glutamate dehydrogenase, were measured in second-flush needles of 1989, harvested in November of 1989. Root collar diameter growth rate was also determined. Variation in depth to soil mottling, an indicator of changing redox conditions, significantly affected tree growth and nitrogen metabolism. Therefore depth to soil mottling was used as a covariate and dose-response curves were provided with adjusted means. A decline of root collar diameter growth rate and foliar chlorophyll content was found at the highest ozone level. However, both these parameters were affected much more by soil conditions than by ozone. Glutamine synthetase, glutamate dehydrogenase and amino acids, especially glutamate and glutamine, increased by approx. 2-fold and 3-fold, respectively, at two and three times ambient ozone. However, soluble protein content was only affected at the highest ozone concentration, showing a 2-5-fold increase. Nitrogen metabolism was more influenced by ozone than by the variation in edaphic conditions. No consistent ozone X family interaction on nitrogen metabolism could be found, but the two half-sib families significantly differed in glutamate dehydrogenase activity and the contents of glutamate and glycine, indicating a regulatory function of this enzyme between nitrogen and carbon metabolism. The increase of amino-N turnover and the following rise in soluble protein content are explained by the strategy of the plant to reallocate the nutrients from needles subjected to accelerated senescence by ozone. Possible implications of this process in carbohydrate metabolism and carbon partitioning are discussed.

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Evidence for Metabolic Domains within the Matrix Compartment of Pea Leaf Mitochondria

Cited by 40 publications

References 25 publications

The Free NADH Concentration Is Kept Constant in Plant Mitochondria under Different Metabolic Conditions

The Free NADH Concentration Is Kept Constant in Plant Mitochondria under Different Metabolic Conditions

Light Regulation of Leaf Mitochondrial Pyruvate Dehydrogenase Complex

Effects of ozone on foliar nitrogen metabolism of Pinus taeda L. and implications for carbohydrate metabolism

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