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In Arabidopsis thaliana, enzymes of glycolysis are present on the surface of mitochondria and free in the cytosol. The functional significance of this dual localization has now been established by demonstrating that the extent of mitochondrial association is dependent on respiration rate in both Arabidopsis cells and potato (Solanum tuberosum) tubers. Thus, inhibition of respiration with KCN led to a proportional decrease in the degree of association, whereas stimulation of respiration by uncoupling, tissue ageing, or overexpression of invertase led to increased mitochondrial association. In all treatments, the total activity of the glycolytic enzymes in the cell was unaltered, indicating that the existing pools of each enzyme repartitioned between the cytosol and the mitochondria. Isotope dilution experiments on isolated mitochondria, using (13)C nuclear magnetic resonance spectroscopy to monitor the impact of unlabeled glycolytic intermediates on the production of downstream intermediates derived from (13)C-labeled precursors, provided direct evidence for the occurrence of variable levels of substrate channeling. Pull-down experiments suggest that interaction with the outer mitochondrial membrane protein, VDAC, anchors glycolytic enzymes to the mitochondrial surface. It appears that glycolytic enzymes associate dynamically with mitochondria to support respiration and that substrate channeling restricts the use of intermediates by competing metabolic pathways.

Original publication

DOI

10.1105/tpc.107.053371

Type

Journal article

Journal

Plant Cell

Publication Date

11/2007

Volume

19

Pages

3723 - 3738

Keywords

Arabidopsis, Cell Respiration, Fructose-Bisphosphate Aldolase, Glycolysis, Magnetic Resonance Spectroscopy, Mitochondria, Molecular Weight, Oxidation-Reduction, Pentose Phosphate Pathway, Plant Proteins, Protein Binding, Solanum tuberosum, Substrate Specificity