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Oxoglutarate dehydrogenase



2-oxoglutarate dehydrogenase E1 component (α-Ketoglutarate dehydrogenase)
Symbol(s): OGDH
Other names: Alpha-ketoglutarate dehydrogenase
Genetic data
Locus: Chr. 7 p13-p11.2
Gene type: protein coding
Protein Structure/Function
Molecular Weight: 115942 (Da)
Protein type: Enzyme: Dehydrogenase
Functions: converts Alpha ketoglutarate to succinyl CoA
Domains: Transketolase central region, Dehydrogenase E1 component
Other
Taxa expressing:Homo sapiens; homologs: ubiquitous among oxidatively respiring organisms
Cell types:ubiquitous among aerobic cells
Subcellular localization:mitochondrion, mitochondrial matrix
Pathway(s):Citric acid cycle, Lysine degradation, Tryptophan metabolism
Enzymatic Data
Catalytic activity:2-oxoglutarate + [dihydrolipoyllysine-residue succinyltransferase] lipoyllysine = [dihydrolipoyllysine-residue succinyltransferase] S-succinyldihydrolipoyllysine + CO(2)
Cofactor(s):Thiamine pyrophosphate lipoate, FAD, NAD, CoA
Enzyme Regulation:Catabolite repressed
Medical/Biotechnological data
Diseases:Alpha-Ketoglutarate Dehydrogenase Deficiency
Database Links
EC number: 1.2.4.2
Codes: EntrezGene 4967; Online 'Mendelian Inheritance in Man' (OMIM) 203740; RefSeq NM_001003941; UniProt Q02218

Oxoglutarate dehydrogenase (aka α-ketoglutarate dehydrogenase) is an enzyme complex most commonly known for its role in the citric acid cycle.

Additional recommended knowledge

Contents

Units

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

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

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 branched-chain α-keto acids.

Properties

Nomenclature and classification

The official name of this enzyme is oxoglutarate dehydrogenase (OGDC) although it is also commonly known as α-ketoglutarate dehydrogenase (AKGDH).

  • CAS: 9031-02-1

Metabolic pathways

This enzyme participates in three different pathways:

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+ + CoA → Succinyl CoA + CO2 + NADH
 

This reaction proceeds in three steps:

  • decarboxylation of α-ketoglutarate,
  • oxidation,
  • and subsequent transfer to CoA, which forms the end product, succinyl CoA.

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.


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 inflamatory immune responses. Some of these inflamatory 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.

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.
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Oxoglutarate_dehydrogenase". A list of authors is available in Wikipedia.
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