PMID:18842826

Citation	Araújo, WL, Nunes-Nesi, A, Trenkamp, S, Bunik, VI and Fernie, AR (2008) Inhibition of 2-oxoglutarate dehydrogenase in potato tuber suggests the enzyme is limiting for respiration and confirms its importance in nitrogen assimilation,. Plant Physiol. 148:1782-96
Abstract	The 2-oxoglutarate dehydrogenase complex constitutes a mitochondrially localized tricarboxylic acid cycle multienzyme system responsible for the conversion of 2-oxoglutarate to succinyl-coenzyme A concomitant with NAD(+) reduction. Although regulatory mechanisms of plant enzyme complexes have been characterized in vitro, little is known concerning their role in plant metabolism in situ. This issue has recently been addressed at the cellular level in nonplant systems via the use of specific phosphonate inhibitors of the enzyme. Here, we describe the application of these inhibitors for the functional analysis of the potato (Solanum tuberosum) tuber 2-oxoglutarate dehydrogenase complex. In vitro experiments revealed that succinyl phosphonate (SP) and a carboxy ethyl ester of SP are slow-binding inhibitors of the 2-oxoglutarate dehydrogenase complex, displaying greater inhibitory effects than a diethyl ester of SP, a phosphono ethyl ester of SP, or a triethyl ester of SP. Incubation of potato tuber slices with the inhibitors revealed that they were adequately taken up by the tissue and produced the anticipated effects on the in situ enzyme activity. In order to assess the metabolic consequences of the 2-oxoglutarate dehydrogenase complex inhibition, we evaluated the levels of a broad range of primary metabolites using an established gas chromatography-mass spectrometry method. We additionally analyzed the rate of respiration in both tuber discs and isolated mitochondria. Finally, we evaluated the metabolic fate of radiolabeled acetate, 2-oxoglutarate or glucose, and (13)C-labeled pyruvate and glutamate following incubation of tuber discs in the presence or absence of either SP or the carboxy ethyl ester of SP. The data obtained are discussed in the context of the roles of the 2-oxoglutarate dehydrogenase complex in respiration and carbon-nitrogen interactions.
Links	PubMed PMC2593666 Online version:10.1104/pp.108.126219
Keywords	Carbon Dioxide/metabolism; Enzyme Inhibitors/pharmacology; Esters/pharmacology; Ketoglutarate Dehydrogenase Complex/antagonists & inhibitors; Ketoglutarate Dehydrogenase Complex/physiology; Mitochondria/drug effects; Mitochondria/metabolism; Nitrogen/metabolism; Organophosphonates/pharmacology; Oxygen/metabolism; Plant Proteins/antagonists & inhibitors; Plant Proteins/physiology; Plant Tubers/drug effects; Plant Tubers/enzymology; Plant Tubers/metabolism; Solanum tuberosum/drug effects; Solanum tuberosum/enzymology; Solanum tuberosum/metabolism; Succinates/pharmacology
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
SOLTU:Q9FEN7	enables	GO:0034602: oxoglutarate dehydrogenase (NAD+) activity	ECO:0000314: direct assay evidence used in manual assertion		F		Seeded From UniProt	complete
SOLTU:Q9FEN7		GO:1901857: positive regulation of cellular respiration	ECO:0000314:		P		Fig 4 and Table 2, Fig 5	complete CACAO 6754
SOLTU:Q9FEN7		GO:0090352: regulation of nitrate assimilation	ECO:0000314:		P		Fig 8	complete CACAO 6755
SOLTU:Q9FEN7		GO:0006521: regulation of cellular amino acid metabolic process	ECO:0000314:		P		Fig 7	complete CACAO 6756
SOLTU:Q9FEN7		GO:0034602: oxoglutarate dehydrogenase (NAD+) activity	ECO:0000314:		F		Fig 3	complete CACAO 6757

References

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