Carbon Dioxide Fixation into Oxalacetate in Higher Plants.

Mazelis, Mendel; Vennesland, Birgit

doi:10.1104/pp.32.6.591

Cited by 101 publications

(39 citation statements)

References 21 publications

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“…The homogenate was then centrifuged at 10,000g for 10 min at 4 C and virtually all proteins were precipitated as phenol-protein complexes (15). Re-extraction of the pellet with 3% Triton X-100 (v/v) Mazelis and Vennesland (22). The reaction mixture contained 0.5 ml of enzyme solution, 5 /umoles of OAA, 2.5 /tmoles of ATP, 50 umoles of NaH"CO. (0.013 /Xi/p!mole), 2 , moles of MnCl,, 4 ,umoles of GSH, and 250…”

Section: Methodsmentioning

confidence: 99%

“…All enzymatic activities are expressed on a per-gram-freshweight basis, because the high concentration of phenolic substances in grapes (28) causes serious interference with the common methods of protein determination (21 (3,7,9,22). In addition, PEP carboxylase has little or no activity at pH 6, whereas PEP carboxykinase at this pH has considerable activity (7,9), with the optimum pH ranging between 6.4 and 6.7 (20).…”

Section: Methodsmentioning

confidence: 99%

“…tive direction is PEP-carboxykinase (EC 4.1.1.32) (3). This enzyme has been found in plant seeds (5) and in a limited number of other higher plants (7,9,22), but not in grape berries (23).…”

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confidence: 99%

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Phosphoenolpyruvate Carboxykinase Activity in Grape Berries

Ruffner

Kliewer²

1975

Plant Physiol.

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Phosphoenolpyruvate (PEP) carboxykinase activity was found in crude extracts of 'Pinot noir' grape berries. The enzyme required ATP, Mn'+ plus Mg, a pH of 6.6, and a temperature of 40 C for maximum activity. The range in concentration of oxaloacetic acid needed for maximum phosphoenolpyruvate carboxykinase activity was 5 to 10 mM, and the Km for HC03-in the exchange of 1CO2 into oxaloacetic acid was 26.8 mM.Changes in the activity of PEP carboxykinase and PEP carboxylase in berries were studied at weekly intervals throughout fruit development. PEP carboxykinase had maximum activity 4 weeks after flowering, and during the following 11 weeks remained relatively constant. The activity of PEP carboxylase was 2-to 4-fold higher than PEP carboxykinase throughout fruit development, and changed little except for a sharp reduction at the onset of ripening.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Phosphoenolpyruvate Carboxykinase Activity in Grape Berries

Ruffner

Kliewer²

1975

Plant Physiol.

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“…The malate level in plants is generally high and is thought to function sometimes as an intermediary storage carbohydrate in the cell vacuole [53,54]. Under conditions of low glycolysis and slow turnover of the citric acid cycle, found for example in dormant plant tissue, the exogenous malic enzyme might oxidise the stored malate via the respiratory chain, thus supplying a limited amount of energy and conserving a large proportion of the carbon skeleton, which can function as a precursor in biosynthesis of lipids and amino acids.…”

Section: Cellular Aspects Of Mitochondria1mentioning

confidence: 99%

The Oxidation of Malate by Isolated Plant Mitochondria

Coleman

Palmer

1972

European Journal of Biochemistry

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The functional relationship between NAD+-linked oxidations of L-malate and the operation of the exogenous and endogenous NADH dehydrogenases of isolated plant mitochondria have been investigated.1. Mitochondria isolated from tubers of the Jerusalem artichoke (Helianthus tuberosus) oxidised L-malate via an electron transport pathway which was inhibited by rotenone, piericidin A and added oxaloacetate. Phosphorylation linked to this pathway yielded an APD/O ratio of approx. 3.2. I n the presence of rotenone, piericidin A or added oxaloacetate, malate was oxidised by a pathway which was dependent on the presence of added NAD+ and low levels ofCa2+. Phosphorylation linked to this oxidation had an ADP/O ratio of approx. 2.3. Oxidation of malate via the rotenone-sensitive pathway was inhibited by 2-n-butylmalonate whereas oxidation via the rotenone-insensitive pathway was unaffected by this compound. 4.By following the reduction of ferricyanide by malate in intact mitochondria, it was possible to identify two separate malate ; NAD oxidoreductases ; one located outside the inner membrane permeability barrier, the other inside this barrier.5. oxaloacetate was the primary product when malate was oxidised by the enzyme in the inner compartment which was therefore identified as L-malate ; NAD oxidoreductase whereas pyruvate was the primary product of malate oxidation by the enzyme in the outer compartment, which was identified as L-malate ; NAD oxidoreductase (decarboxylating) or malic enzyme.6. The malic enzyme was extracted and partially purified from isolated mitochondria. The isolated enzyme showed a requirement for Mn2+ or Mg2+, required NAD+ as coenzyme, although activity to a lesser extent was obtained with NADP+. and was inhibited by NADH.7. It was concluded that in intact plant mitochondria there were two pathways by which malate can be oxidised : in the inner compartment via malate dehydrogenase in association with the endogenous NADH dehydrogenase system and in the intermembrane compartment via NADf-linked malic enzyme associated with the exogenous NADH dehydrogenase system. The implications these findings are discussed.L-Malate is poorly oxidised by malate dehydrogenase in animal mitochondria unless the oxaloacetate formed as a product is removed, by either transamination with glutamate or by condensation with acetyl-CoA [I -31. I n contrast isolated plant mitochondria will rapidly oxidise malate in the absence of added oxaloacetate-removing agents [4-71. shown that in cauliflower bud mitochondria, pyruvate was a direct product of malate oxidation by a NAD+-requiring malic enzyme, which showed a dependence on added NAD+ and was linked to the electron transport chain [ll].Abbreviations. EGTA, ethyleneglycol bis

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“…CO2 + ADP + PEP+&I% +OAA + ATP (1) In addition, PEPCK catalyzes a nucleotide-dependent exchange of CO2 into OAA (16,20).…”

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confidence: 99%

Characterization of Phosphoenolpyruvate Carboxykinase from Panicum maximum

Ray¹,

Black²

1976

Plant Physiol.

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PEPCK has been characterized from several microorganisms and animals (1, 5-7, 9). However, only limited information is available on the characteristics of this enzyme in higher plants and most of this has been obtained using crude extracts (2, 10-14, 16, 18). In addition, the data on plant PEPCK are on either the exchange reaction or the ADP-dependent carboxylation reaction. Using either of these reactions to study PEPCK in relation to C4 photosynthesis is open to criticism since the proposed role of PEPCK is as a decarboxylase. The exchange reaction has been found to occur at rates much faster (3-to 30-fold) than either the carboxylation or decarboxylation reaction in animal tissue (7) Even though PEPCK is proposed as the decarboxylase in bundle sheath cells of certain C4 plants, no information is available on the characteristics of the ATP-dependent decarboxylation of OAA by the enzyme (12)(13)(14). This report presents data on the partial purification of PEPCK to remove PEP carboxylase using the C4 grass Panicum maxinum. The ATP-dependent decarboxylation reaction has been characterized and compared to the exchange reaction and the ADP-dependent carboxylation reaction.Phosphoenolpyruvate carboxykinase catalyzes the nucleotidedependent carboxylation of PEP2 to produce OAA in a reversible fashion as shown in equation 1. CO2 + ADP + PEP+&I% +OAA + ATP (1) In addition, PEPCK catalyzes a nucleotide-dependent exchange of CO2 into OAA (16,20).PEPCK has been proposed to act as a decarboxylase during photosynthesis in bundle sheath cells of specific plants which carry out C4 photosynthesis such as Panicum maximum. Through the action of PEPCK in these C4 plants, CO2 is released from OAA in the bundle sheath cells where the CO2 is refixed by the C3 cycle (3,12,14). In other C4 plants either a NADP+-or NAD+-dependent malic enzyme acts as the decarboxylase in bundle sheath cells. In all C4 plants the 4-carbon organic acids 1

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Carbon Dioxide Fixation into Oxalacetate in Higher Plants.

Cited by 101 publications

References 21 publications

Phosphoenolpyruvate Carboxykinase Activity in Grape Berries

Phosphoenolpyruvate Carboxykinase Activity in Grape Berries

The Oxidation of Malate by Isolated Plant Mitochondria

Characterization of Phosphoenolpyruvate Carboxykinase from Panicum maximum

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