OGDH (Oxoglutarate Dehydrogenase) encodes the E1 subunit (alpha-ketoglutarate dehydrogenase) of the alpha-ketoglutarate dehydrogenase complex (α-KGDH), a key mitochondrial enzyme in the tricarboxylic acid (TCA) cycle. Located on chromosome 7p13, OGDH catalyzes the oxidative decarboxylation of α-ketoglutarate to succinyl-CoA, producing NADH and CO2. This reaction is the second NADH-producing step in the TCA cycle and is essential for cellular energy metabolism.
| Property | Value |
|---|---|
| Gene Symbol | OGDH |
| Full Name | Oxoglutarate Dehydrogenase |
| Chromosomal Location | 7p13 |
| NCBI Gene ID | 4967 |
| OMIM ID | 203740 |
| Ensembl ID | ENSG00000105953 |
| UniProt ID | Q02218 |
| Encoded Protein | OGDH (α-KGDH E1) |
| Gene Type | Protein-coding |
| Protein Family | 2-oxoacid dehydrogenase family |
| Associated Diseases | Alzheimer's disease, Parkinson's disease, 2-hydroxyglutaric aciduria |
OGDH is a critical metabolic enzyme whose activity is significantly reduced in aging brain and in neurodegenerative diseases including Alzheimer's disease (AD) and Parkinson's disease (PD). The enzyme is particularly vulnerable to oxidative stress, creating a feed-forward cycle of mitochondrial dysfunction in neurodegeneration.
OGDH is the E1alpha subunit of the α-KGDH complex [1]:
The enzyme requires thiamine pyrophosphate (TPP) as an essential cofactor, coordinating at the active site with Mg2+ and participating in decarboxylation.
The α-KGDH complex is a multienzyme assembly:
| Subunit | Gene | Function |
|---|---|---|
| E1α | OGDH | Oxidative decarboxylation |
| E1β | OGDHL1 | Dihydrolipoyl dehydrogenase |
| E2 | DLST | Dihydrolipoamide succinyltransferase |
| E3 | DLD | Lipoamide dehydrogenase |
The reaction catalyzed by α-KGDH:
α-ketoglutarate + CoA + NAD+ → succinyl-CoA + NADH + CO2
This reaction:
α-KGDH occupies a critical position in the TCA cycle [2]:
In neurons, α-KGDH serves additional functions [3]:
The enzyme is tightly regulated:
| Regulator | Effect | Mechanism |
|---|---|---|
| NADH/NAD+ ratio | Inhibition | Product inhibition |
| ATP | Inhibition | Energy sensing |
| Succinyl-CoA | Inhibition | Product inhibition |
| ROS | Inhibition | Oxidative damage |
| Thiamine | Protection | Cofactor availability |
OGDH activity is significantly reduced in AD brain [4] [5]:
Reduced activity in AD:
Mechanisms of reduction:
OGDH deficiency in PD [6]:
Vulnerability factors:
α-KGDH is highly sensitive to oxidative stress [7]:
Reduced α-KGDH leads to:
The enzyme interacts with:
| Enzyme | Interaction | Consequence |
|---|---|---|
| Complex I | Sequential NADH production | Combined deficiency |
| PDH | Parallel pathway | Metabolic shunting |
| IDH | α-ketoglutarate pool | Feedback regulation |
OGDH mutations cause 2-hydroxyglutaric aciduria [8]:
OGDH acts as a tumor suppressor in cancer [9]:
Therapeutic approaches:
Thiamine supplementation
Antioxidant approaches
Metabolic modulators
Gene therapy
| Brain Region | Expression Level | Significance |
|---|---|---|
| Cortex | High | High metabolic demand |
| Hippocampus | High | Memory circuits |
| Substantia nigra | Moderate | Dopaminergic neurons |
| Cerebellum | Moderate | Motor coordination |
| Protein/Pathway | Interaction Type | Relevance |
|---|---|---|
| DLST | Complex assembly | E2 subunit |
| DLD | Complex assembly | E3 subunit |
| Complex I | Sequential | ETC function |
| PDH | Parallel | TCA regulation |
| IDH | Substrate shared | α-KG pool |
| Thiamine | Cofactor | Enzymatic activity |
OGDH complex structure and function. Biochimica et Biophysica Acta. 2012. ↩︎
Alpha-ketoglutarate dehydrogenase in brain bioenergetics. Journal of Neuroscience Research. 2016. ↩︎
OGDH and succinyl-CoA in neurotransmitter synthesis. Neurochemical Research. 2020. ↩︎
OGDH dysfunction in Alzheimer's disease. Journal of Alzheimer's Disease. 2019. ↩︎
Mitochondrial abnormalities in Alzheimer disease. Neurochemical Research. 2005. ↩︎
Mitochondrial OGDH deficiency in PD. Neurobiology of Disease. 2015. ↩︎
Alpha-KGDH in neurodegeneration and aging. Advances in Neurobiology. 2018. ↩︎
OGDH mutations and 2-hydroxyglutaric aciduria. Brain. 2012. ↩︎
OGDH deficiency and cancer metabolism. Cell Cycle. 2012. ↩︎