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Oxoglutarate dehydrogenase

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Oxoglutarate dehydrogenase

oxoglutarate dehydrogenase
Identifiers
EC number CAS number IntEnz BRENDA ExPASy KEGG MetaCyc metabolic pathway
PRIAM PDB structures PDBsum
Gene Ontology EGO

The oxoglutarate dehydrogenase complex (OGDC) or α-ketoglutarate dehydrogenase complex is an enzyme complex, most commonly known for its role in the citric acid cycle.

Units

Much like pyruvate dehydrogenase complex (PDC), this enzyme forms a complex composed of three components:

Unit EC number Name Gene Coenzyme
E1 1.2.4.2 oxoglutarate dehydrogenase OGDH thiamine pyrophosphate
E2 2.3.1.61 dihydrolipoyl succinyltransferase DLST lipoic acid
E3 1.8.1.4 dihydrolipoyl dehydrogenase DLD FAD

In fact, three classes of these multienzyme complexes have been characterized, one specific for pyruvate, a second specific for 2-oxoglutarate, and a third specific for branched-chain α-keto acids.

Properties

Metabolic pathways

This enzyme participates in three different pathways:

  • MAP00020)
  • MAP00310)
  • MAP00380)

Kinetic properties

The following values are from Azotobacter vinelandii (1):

  • KM: 0.14 ± 0.04 mM
  • Vmax : 9 ± 3 μmol.min-1.mg-1

Citric acid cycle

Reaction

The reaction catalyzed by this enzyme in the citric acid cycle is:

α-ketoglutarate + NAD+ + CoASuccinyl CoA + CO2 + NADH

This reaction proceeds in three steps:

ΔG°' for this reaction is -7.2 kcal mol-1. The energy needed for this oxidation is conserved in the formation of a thioester bond of succinyl CoA.

Regulation

Oxoglutarate dehydrogenase is a key control point in the citric acid cycle. It is inhibited by its products, succinyl CoA and NADH. A high energy charge in the cell will also be inhibitive. ADP and calcium ions are allosteric activators of the enzyme.

Pathology

2-Oxo-glutarate dehydrogrenase is an autoantigen recognized in primary biliary cirrhosis, a form of acute liver failure. These antibodies appear to recognize oxidized protein that has resulted from inflammatory immune responses. Some of these inflammatory responses are explained by gluten sensitivity.[1] Other mitochondrial autoantigens include pyruvate dehydrogenase and branched-chain alpha-keto acid dehydrogenase complex, which are antigens recognized by anti-mitochondrial antibodies. Activity of the 2-oxoglutarate dehydrogenase complex is decreased in many neurodegenerative diseases.

References

  1. Bunik V, Westphal AH, de Kok A: Kinetic properties of the 2-oxoglutarate dehydrogenase complex from Azotobacter vinelandii evidence for the formation of a precatalytic complex with 2-oxoglutarate. Eur J Biochem 2000; 267(12): 3583-91. PMID 10848975.
  2. Bunik VI, Strumilo S: "Regulation of Catalysis Within Cellular Network: Metabolic and Signaling Implications of the 2-Oxoglutarate Oxidative Decarboxylation." Current Chemical Biology, 2009, 3: 279-290
  3. Bunik VI, Fernie AR: "Metabolic control exerted by the 2-oxoglutarate dehydrogenase reaction: a cross-kingdom comparison of the crossroad between energy production and nitrogen assimilation." Biochem. J. 2009, 422: 405–421
  4. L. Trofimova, M. Lovat, A. Groznaya, E. Efimova, T. Dunaeva, M. Maslova, A. Graf, and V. Bunik: "Behavioral Impact of the Regulation of the Brain 2-Oxoglutarate Dehydrogenase Complex by Synthetic Phosphonate Analog of 2-Oxoglutarate: Implications into the Role of the Complex in Neurodegenerative Diseases." International Journal of Alzheimer Disease 2010; Volume 2010, Article ID 749061, 8 pages, http://www.sage-hindawi.com/journals/ijad/2010/749061.html

External links

  • Medical Subject Headings (MeSH)

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