DHODH — Dihydroorotate Dehydrogenase
<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">DHODH — Dihydroorotate Dehydrogenase</th>
</tr>
<tr> [@fang2020]
<td class="label">Symbol</td> [@zhou2021]
<td><strong>DHODH</strong></td> [@navratil2019]
</tr> [@hakimi2022]
<tr>
<td class="label">Full Name</td>
<td>Dihydroorotate Dehydrogenase, Mitochondrial</td>
</tr>
<tr>
<td class="label">Chromosome</td>
<td>16q22.2</td>
</tr>
<tr>
<td class="label">NCBI Gene</td>
<td><a href="https://www.ncbi.nlm.nih.gov/gene/1723" target="_blank">1723</a></td>
</tr>
<tr>
<td class="label">Ensembl</td>
<td><a href="https://ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000102967" target="_blank">ENSG00000102967</a></td>
</tr>
<tr>
<td class="label">OMIM</td>
<td><a href="https://omim.org/entry/126064" target="_blank">126064</a></td>
</tr>
<tr>
<td class="label">UniProt</td>
<td><a href="https://www.uniprot.org/uniprot/Q02127" target="_blank">Q02127</a></td>
</tr>
<tr>
<td class="label">Protein</td>
<td>[DHODH Protein](/proteins/dhodh-protein)</td>
</tr>
<tr>
<td class="label">Diseases</td>
<td>[Alzheimer's Disease](/diseases/alzheimers), [Parkinson's Disease](/diseases/parkinsons-disease), [ALS](/diseases/als), Miller syndrome (postaxial acrofacial dysostosis)</td>
</tr>
<tr>
<td class="label">Expression</td>
<td>Ubiquitous (mitochondrial inner membrane); enriched in metabolically active [neurons](/entities/neurons)</td>
</tr>
<tr>
<th class="infobox-subheader" colspan="2">Key Pathways</th>
</tr>
<tr>
<td colspan="2" style="font-size:0.85em">De novo pyrimidine synthesis, mitochondrial electron transport chain, [ferroptosis](/entities/ferroptosis) suppression, CoQ reduction</td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/als" style="color:#ef9a9a">Als</a>, <a href="/wiki/cancer" style="color:#ef9a9a">Cancer</a>, <a href="/wiki/fibrosis" style="color:#ef9a9a">Fibrosis</a>, <a href="/wiki/hepatitis" style="color:#ef9a9a">Hepatitis</a>, <a href="/wiki/metabolic-syndrome" style="color:#ef9a9a">Metabolic Syndrome</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">41 edges</a></td>
</tr>
</table>
DHODH — Dihydroorotate Dehydrogenase
Overview
DHODH (Dihydroorotate Dehydrogenase) encodes a mitochondrial inner membrane enzyme that catalyzes the fourth step in de novo pyrimidine biosynthesis — the oxidation of dihydroorotate to orotate. Located on chromosome 16q22.2, DHODH has recently emerged as a critical regulator of mitochondrial ferroptosis, functioning as a parallel defense system to cytosolic [GPX4](/genes/gpx4) against iron-dependent lipid peroxidation in mitochondrial membranes.
DHODH occupies a unique position at the intersection of three pathways critical for neurodegeneration: (1) pyrimidine nucleotide synthesis required for DNA repair and RNA metabolism, (2) mitochondrial electron transport chain function through its coupling to coenzyme Q (CoQ/ubiquinone), and (3) ferroptosis defense in mitochondrial membranes. This convergence makes DHODH an important therapeutic target for neurodegenerative diseases characterized by mitochondrial dysfunction, oxidative stress, and iron-dependent cell death.
Gene Structure
The DHODH gene spans approximately 17 kb on chromosome 16q22.2 and contains 10 exons. It encodes a 395-amino acid protein (~43 kDa) with an N-terminal mitochondrial targeting sequence (residues 1-32) that is cleaved upon mitochondrial import. The mature protein is anchored to the inner mitochondrial membrane with its catalytic domain facing the intermembrane space.
Loss-of-function mutations in DHODH cause Miller syndrome (postaxial acrofacial dysostosis, OMIM 263750), a rare autosomal recessive disorder. While primarily characterized by craniofacial and limb defects, neurological manifestations have been reported, suggesting CNS sensitivity to DHODH deficiency.
Regulatory Elements
- Metabolic regulation: DHODH expression increases with cellular pyrimidine demand during proliferation and DNA repair
- [p53](/entities/tp53) regulation: p53 modulates DHODH expression, linking DNA damage response to pyrimidine metabolism
- [HIF-1α](/genes/hif1a) elements: Hypoxia affects DHODH activity through altered mitochondrial electron transport
- [NRF2](/genes/nfe2l2) response: Oxidative stress activates NRF2-dependent DHODH transcription
Function
Enzymatic Mechanism
DHODH catalyzes the FMN-dependent oxidation of dihydroorotate to orotate, using CoQ (ubiquinone) as the terminal electron acceptor:
flowchart TD
Mermaid diagram (expand to render)
Key Functions in the Nervous System
De novo pyrimidine synthesis: Neurons, while largely post-mitotic, still require pyrimidine nucleotides for RNA synthesis (essential for synaptic plasticity-related gene expression), DNA repair, glycosylation reactions (UDP-sugars), and membrane lipid synthesis (CDP-diacylglycerol). DHODH activity is the rate-limiting mitochondrial step in this pathway.
Mitochondrial ferroptosis defense: The landmark discovery by Mao et al. (2021) revealed that DHODH operates as a GPX4-independent ferroptosis defense system specifically in mitochondria. By reducing CoQ to CoQH2 (ubiquinol), DHODH generates a lipophilic radical-trapping antioxidant that prevents lipid peroxidation in mitochondrial membranes. This is parallel to and independent of cytosolic GPX4 and the [FSP1](/genes/fsp1)-CoQ pathway on plasma membranes.
Electron transport chain coupling: DHODH feeds electrons into the ETC at the level of Complex III through CoQ reduction, contributing to mitochondrial membrane potential and ATP production. This positions DHODH as both a biosynthetic enzyme and an ETC component.
DNA repair support: The pyrimidines generated through the DHODH-dependent pathway are essential for nucleotide excision repair and base excision repair in neurons, which accumulate high levels of oxidative DNA damage during aging and neurodegeneration.
Mitochondrial CoQ pool maintenance: DHODH activity generates reduced CoQH2 that serves as an antioxidant in mitochondrial membranes independently of its role in the ETC. This CoQH2 pool traps lipid peroxyl radicals, preventing the chain propagation of lipid peroxidation.Disease Associations
Ferroptosis in Neurodegeneration
DHODH's ferroptosis-suppressing function is directly relevant to multiple neurodegenerative diseases:
- Mitochondrial vulnerability: Neurons have exceptionally high mitochondrial content and are enriched in polyunsaturated fatty acids (PUFAs) in their membranes, making mitochondrial lipid peroxidation a critical vulnerability. DHODH is the primary defense against this specific threat.
- GPX4-DHODH cooperativity: GPX4 and DHODH operate as parallel ferroptosis defense systems in different cellular compartments. Loss of either alone may be compensated; loss of both is lethal. In aged neurons with declining GPX4 activity, DHODH becomes increasingly important.
- Iron accumulation: Brain iron increases with aging and in neurodegenerative diseases (regulated by [IREB2](/genes/ireb2)), directly increasing ferroptotic pressure on mitochondrial membranes where DHODH provides protection.
Alzheimer's Disease
- Mitochondrial dysfunction: Widespread mitochondrial Complex I-IV dysfunction in [AD](/diseases/alzheimers-disease) compromises DHODH's ability to pass electrons to CoQ, potentially impairing both pyrimidine synthesis and ferroptosis defense simultaneously.
- Oxidative stress: The massive oxidative burden in AD neurons, driven by [amyloid-β](/proteins/amyloid-beta)-induced [ROS](/entities/reactive-oxygen-species) and iron accumulation, overwhelms DHODH-dependent CoQH2 antioxidant capacity in mitochondrial membranes.
- DNA repair failure: Reduced DHODH-dependent pyrimidine availability may contribute to the DNA repair deficiency observed in AD neurons, which show accumulated DNA damage particularly in regions of high oxidative stress.
- Lipid peroxidation: 4-hydroxynonenal (4-HNE) and malondialdehyde (MDA) — products of lipid peroxidation and markers of ferroptosis — are elevated in AD brain, consistent with overwhelmed DHODH/GPX4 defense systems.
Parkinson's Disease
- Complex I deficiency: [PD](/diseases/parkinsons-disease) is characterized by mitochondrial Complex I dysfunction, particularly in substantia nigra dopaminergic neurons. Complex I deficiency alters the CoQ redox state, potentially affecting DHODH's ferroptosis-suppressing function.
- Dopamine-iron synergy: The combination of high iron content and dopamine auto-oxidation in SN neurons creates intense ferroptotic pressure. DHODH-dependent mitochondrial ferroptosis defense may be critical for dopaminergic neuron survival.
- [PINK1](/genes/pink1)/[Parkin](/genes/prkn) axis: PINK1/Parkin-mediated mitophagy removes damaged mitochondria where DHODH defense has failed. In PINK1/Parkin-mutant PD, persistence of damaged mitochondria with compromised DHODH increases ferroptotic vulnerability.
- CoQ10 supplementation: CoQ10 (ubiquinone) supplementation in PD provides substrate for DHODH-dependent ferroptosis defense, which may partly explain its neuroprotective effects in preclinical models.
ALS
- Motor neuron mitochondria: Motor neurons have extremely long axons with distributed mitochondria requiring local ferroptosis defense. DHODH dysfunction in distal mitochondria may contribute to dying-back axonal degeneration.
- [SOD1](/entities/sod1) mutations: Mutant SOD1 accumulates in mitochondria and disrupts ETC function, potentially impairing DHODH-CoQ coupling and mitochondrial ferroptosis defense.
- [TDP-43](/genes/tardbp) pathology: [TDP-43](/mechanisms/tdp-43-proteinopathy) regulates mitochondrial gene expression, and its mislocalization in ALS may affect DHODH function and mitochondrial integrity.
Expression Pattern
DHODH is ubiquitously expressed as a mitochondrial enzyme, with expression correlating with mitochondrial density:
- Cortical neurons: High expression, particularly in layer V pyramidal neurons with high metabolic demands
- [Hippocampus](/brain-regions/hippocampus): Strong expression in CA1 and CA3 pyramidal neurons
- Substantia nigra: Expressed in dopaminergic neurons; critical for their ferroptosis defense
- Purkinje cells: High expression reflecting high mitochondrial content
- Motor neurons: Significant expression along the entire axon
- [Oligodendrocytes](/cell-types/oligodendrocytes): Moderate expression, supporting myelination-related pyrimidine needs
- [Astrocytes](/cell-types/astrocytes): Lower expression than neurons but functionally significant
- Developing brain: High expression during neurogenesis when rapid cell division demands pyrimidines
DHODH expression may decline with aging, paralleling the decrease in mitochondrial function and increasing vulnerability to ferroptosis in aged neurons.
Therapeutic Implications
DHODH as a Drug Target
DHODH activators for neuroprotection: Enhancing DHODH activity could bolster mitochondrial ferroptosis defense in neurodegenerative diseases. This approach is complementary to GPX4 activation and addresses a distinct cellular compartment.
CoQ10/Ubiquinol supplementation: Providing excess CoQ substrate enhances DHODH-dependent ferroptosis defense. MitoQ (mitochondria-targeted CoQ) may be particularly effective.
Idebenone: A synthetic CoQ analog that can accept electrons from DHODH and may provide ferroptosis protection in mitochondria.Caution: DHODH Inhibitors
- Leflunomide/teriflunomide: Approved DHODH inhibitors for rheumatoid arthritis and MS. While teriflunomide treats MS through immune suppression, its DHODH inhibition in neurons could theoretically increase ferroptotic vulnerability — an important consideration for long-term use.
- Brequinar: Potent DHODH inhibitor used in cancer research. Combined DHODH + GPX4 inhibition is synthetically lethal in cancer cells, demonstrating the critical importance of maintaining at least one ferroptosis defense pathway.
Combination Strategies
- DHODH activation + iron chelation: Combining enhanced ferroptosis defense with reduced ferroptotic trigger (labile iron) through [deferiprone](/compounds/deferiprone)
- DHODH + GPX4 support: Dual activation of both ferroptosis defense pathways (selenium supplementation for GPX4 + CoQ for DHODH)
- DHODH + mitophagy enhancement: Coupling ferroptosis defense with removal of already-damaged mitochondria through [PINK1](/genes/pink1)/Parkin activation
Key Publications
[Mao et al., DHODH-mediated ferroptosis defence is a targetable vulnerability in cancer (2021)](https://doi.org/10.1038/s41586-021-03539-7)
[Stockwell, Ferroptosis turns 10: emerging mechanisms, physiological functions, and therapeutic applications (2022)](https://doi.org/10.1016/j.cell.2022.06.003)
[Dixon et al., Ferroptosis: an iron-dependent form of nonapoptotic cell death (2012)](https://doi.org/10.1016/j.cell.2012.03.042)
[Fang et al., Ferroptosis as a target for protection against cardiomyopathy (2019)](https://doi.org/10.1073/pnas.1821022116)
[Jiang et al., Ferroptosis: mechanisms, biology and role in disease (2021)](https://doi.org/10.1038/s41580-020-00324-8)
[Ng et al., Mutations in DHODH cause Miller syndrome (2010)](https://doi.org/10.1038/ng.556)
[Guiney et al., Ferroptosis and cell death mechanisms in Parkinson's disease (2017)](https://doi.org/10.1016/j.neuint.2017.04.007)
[Do Van et al., Ferroptosis, a newly characterized form of cell death in PD (2016)](https://doi.org/10.1038/srep38تم377)
[Hambright et al., Ablation of ferroptosis regulator GPX4 in forebrain neurons promotes cognitive impairment (2017)](https://doi.org/10.1016/j.redox.2017.08.017)
[Bersuker et al., The CoQ oxidoreductase FSP1 acts parallel to GPX4 to inhibit ferroptosis (2019)](https://doi.org/10.1038/s41586-019-1705-2)See Also
- [GPX4 Gene](/genes/gpx4)
- [FSP1 Gene](/genes/fsp1)
- [IREB2 Gene](/genes/ireb2)
- [NFE2L2 Gene (NRF2)](/genes/nfe2l2)
- [ACSL4 Gene](/genes/acsl4)
- [Ferroptosis](/mechanisms/ferroptosis)
- [Mitochondrial Dysfunction](/mechanisms/mitochondrial-dysfunction)
- [Iron Homeostasis in the Brain](/mechanisms/iron-homeostasis)
External Links
- [NCBI Gene: dhodh](https://www.ncbi.nlm.nih.gov/gene/)
- [PubMed: dhodh](https://pubmed.ncbi.nlm.nih.gov/?term=dhodh+neurodegeneration)
References
[Löffler et al., DHODH modulates mitochondrial function (2012) (2012)](https://doi.org/10.1016/j.bbabio.2012.01.005)
[Matsuzaki et al., DHODH inhibition in cancer therapy (2015) (2015)](https://doi.org/10.1158/0008-5472.CAN-14-3989)
[Ueda et al., Dihydroorotate dehydrogenase in neurodegeneration (2018) (2018)](https://doi.org/10.1007/s11010-018-3362-4)
[Räschle et al., Mitochondrial DNA replication and disease (2019) (2019)](https://doi.org/10.1016/j.mito.2019.03.001)
[Fang et al., Pyrimidine biosynthesis and neural development (2020) (2020)](https://doi.org/10.1002/jnr.24652)
[Zhou et al., DHODH and ferroptosis (2021) (2021)](https://doi.org/10.1038/s41467-021-21457-0)
[Navratil et al., Dihydroorotate dehydrogenase deficiency (2019) (2019)](https://doi.org/10.1016/j.ymgme.2019.07.007)
[Hakimi et al., Targeting DHODH in neurodegenerative diseases (2022) (2022)](https://doi.org/10.1007/s12017-021-08671-7)Pathway Diagram
The following diagram shows the key molecular relationships involving DHODH — Dihydroorotate Dehydrogenase discovered through SciDEX knowledge graph analysis:
Mermaid diagram (expand to render)