Oxoglutarate dehydrogenase

Protbox
Name=2-oxoglutarate dehydrogenase E1 component (α-Ketoglutarate dehydrogenase)
Photo=
Caption=
HGNCid = 8124
Symbol = OGDH
AltSymbols =
Names= Alpha-ketoglutarate dehydrogenase
Chromosome = 7
Arm = p
Band = 13
LocusSupplementaryData = -p11.2
Gene=
Gene_type=protein coding
Protein_length=
Molecular_weight=115942
Structure=
Type=Enzyme: Dehydrogenase
Functions=converts Alpha ketoglutarate to succinyl CoA
Domains= Transketolase central region, Dehydrogenase E1 component
Motifs=
Alternative_products=
Catalytic_activity=2-oxoglutarate + [dihydrolipoyllysine-residue succinyltransferase] lipoyllysine = [dihydrolipoyllysine-residue succinyltransferase] S-succinyldihydrolipoyllysine + CO(2)
Cofactors=Thiamine pyrophosphate lipoate, FAD, NAD, CoA
Enzyme_regulation=Catabolite repressed
Biophysicochemical_properties=
Diseases=Alpha-Ketoglutarate Dehydrogenase Deficiency
Pharmaceuticals=
Biotechnology=
Taxa= "Homo sapiens"; homologs: ubiquitous among oxidatively respiring organisms
Cells= ubiquitous among aerobic cells
Location=mitochondrion, mitochondrial matrix
Mods=
Pathways=Citric acid cycle, Lysine degradation, Tryptophan metabolism
Interactions=
Actions=
Agonists=
Antagonists=
EntrezGene =
OMIM =
RefSeq =
UniProt =
PDB =
ECnumber = 1.2.4.2
Codes= EntrezGene|4967; OMIM|203740; RefSeq|NM_001003941; UniProt|Q02218
Pages=
Review=

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

Units

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

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:
* Citric acid cycle (KEGG link: [http://www.genome.jp/kegg/pathway/map/map00720.html MAP00020] )
* Lysine degradation (KEGG link: [http://www.genome.jp/kegg/pathway/map/map00310.html MAP00310] )
* Tryptophan metabolism (KEGG link: [http://www.genome.jp/kegg/pathway/map/map00380.html MAP00380] )

Kinetic properties

The following values are from "Azotobacter vinelandii" ⁽¹⁾:
*K_M: 0.14 ± 0.04 mM
*V_max : 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,
* reduction of NAD⁺ to NADH,
* 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 inflammatory immune responses. Some ofthese inflammatory responses are explained by gluten sensitivity.cite journal | author = Leung PS, Rossaro L, Davis PA, "et al" | title = Antimitochondrial antibodies in acute liver failure: Implications for primary biliary cirrhosis | journal = Hepatology| volume = 46| issue = | pages = 1436| year = 2007 | pmid = 17657817 | doi = 10.1002/hep.21828] Other mitochondrial autoantigensinclude pyruvate dehydrogenase and branched-chain alpha-keto acid dehydrogenase complex, which are antigens recognized by anti-mitochondrial antibodies.

References

# 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.

External links

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