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Metabolic control and regulation of the tricarboxylic acid cycle in photosynthetic and heterotrophic plant tissues
Author(s) -
ARAÚJO WAGNER L.,
NUNESNESI ADRIANO,
NIKOLOSKI ZORAN,
SWEETLOVE LEE J.,
FERNIE ALISDAIR R.
Publication year - 2012
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.2011.02332.x
Subject(s) - fumarase , aconitase , citric acid cycle , isocitrate dehydrogenase , malate dehydrogenase , biochemistry , biology , citrate synthase , phosphoenolpyruvate carboxylase , branched chain alpha keto acid dehydrogenase complex , context (archaeology) , metabolic pathway , dehydrogenase , pyruvate dehydrogenase complex , succinate dehydrogenase , glyoxylate cycle , photosynthesis , metabolism , enzyme , paleontology
The tricarboxylic acid (TCA) cycle is a crucial component of respiratory metabolism in both photosynthetic and heterotrophic plant organs. All of the major genes of the tomato TCA cycle have been cloned recently, allowing the generation of a suite of transgenic plants in which the majority of the enzymes in the pathway are progressively decreased. Investigations of these plants have provided an almost complete view of the distribution of control in this important pathway. Our studies suggest that citrate synthase, aconitase, isocitrate dehydrogenase, succinyl CoA ligase, succinate dehydrogenase, fumarase and malate dehydrogenase have control coefficients flux for respiration of −0.4, 0.964, −0.123, 0.0008, 0.289, 0.601 and 1.76, respectively; while 2‐oxoglutarate dehydrogenase is estimated to have a control coefficient of 0.786 in potato tubers. These results thus indicate that the control of this pathway is distributed among malate dehydrogenase, aconitase, fumarase, succinate dehydrogenase and 2‐oxoglutarate dehydrogenase. The unusual distribution of control estimated here is consistent with specific non‐cyclic flux mode and cytosolic bypasses that operate in illuminated leaves. These observations are discussed in the context of known regulatory properties of the enzymes and some illustrative examples of how the pathway responds to environmental change are given.