oxoglutarate dehydrogenase complex

Definition

Target type: cellularcomponent

A multi-enzyme complex that catalyzes the oxidative decarboxylation of alpha-ketoglutarate (also known as 2-oxoglutarate) to form succinyl-CoA. The complex comprises multiple copies of three enzymes referred to as E1, E2 and E3: oxoglutarate dehydrogenase (lipoamide) (E1), dihydrolipoamide S-succinyltransferase (E2) and dihydrolipoamide dehydrogenase (E3). Additional proteins may also be present. [PMID:10672230]

The oxoglutarate dehydrogenase complex (OGDH) is a multi-enzyme complex located in the mitochondrial matrix. It plays a crucial role in the citric acid cycle (Krebs cycle) by catalyzing the oxidative decarboxylation of α-ketoglutarate to succinyl-CoA. The complex consists of three enzymes:
1. **α-ketoglutarate dehydrogenase (E1):** This enzyme is a tetramer composed of two α subunits and two β subunits. The α subunits contain the active site for the decarboxylation of α-ketoglutarate, while the β subunits are involved in the binding of thiamine pyrophosphate (TPP) and lipoamide.
2. **Dihydrolipoamide succinyltransferase (E2):** This enzyme is a dimer with a lipoyl domain and a catalytic domain. The lipoyl domain carries the lipoamide cofactor, which is responsible for transferring the succinyl group from the E1 enzyme to the E3 enzyme. The catalytic domain is responsible for the formation of succinyl-CoA.
3. **Dihydrolipoamide dehydrogenase (E3):** This enzyme is a dimer composed of two identical subunits. It contains a flavin adenine dinucleotide (FAD) cofactor, which accepts electrons from the reduced lipoamide cofactor of E2. The electrons are then transferred to NAD+, generating NADH.
The three enzymes work in a sequential manner, with E1 catalyzing the decarboxylation of α-ketoglutarate, E2 transferring the succinyl group to CoA, and E3 regenerating the oxidized form of lipoamide. The complex also contains several regulatory proteins, including the E3 binding protein (E3BP) and the pyruvate dehydrogenase kinase (PDK), which regulate the activity of the OGDH complex.
The OGDH complex is highly regulated by various factors, including substrate availability, product inhibition, and phosphorylation by PDK. This regulation ensures that the flux through the citric acid cycle is tightly controlled to meet the energy needs of the cell.'
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Proteins (1)

Compounds (2)