GO:0004151 dihydroorotase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0004151 (dihydroorotase activity) catalyzes the reversible hydrolysis of (S)-dihydroorotate to N-carbamoyl-L-aspartate, the third step of de novo pyrimidine biosynthesis.
• In humans, dihydroorotase activity resides in the multifunctional CAD protein, which also carries carbamoyl phosphate synthetase and aspartate transcarbamoylase activities.
• CAD-dependent dihydroorotase activity supports cancer cell proliferation and contributes to ferroptosis defence, making it a metabolic vulnerability in tumors.
• Oncogenic viruses and oncoproteins such as HUWE1 and PFKFB3 stimulate de novo pyrimidine synthesis by acting on CAD, indirectly elevating dihydroorotase flux.
• In hepatocellular carcinoma, CAD manipulates a tumor-intrinsic DHO/UBE4B/NF-kB pathway that fuels macrophage cross-talk and metastasis.
• Dihydroorotase is a validated drug target in protozoan parasites; orotate analogs inhibit dihydroorotase and dihydroorotate dehydrogenase with antimalarial activity.
Description
Dihydroorotase activity (GO:0004151) is a molecular function defined as the catalysis of the reaction (S)-dihydroorotate + H2O = N-carbamoyl-L-aspartate + H+, a central step in the de novo biosynthesis of pyrimidine nucleotides. This activity is essential because pyrimidines are required for DNA and RNA synthesis, phospholipid and sialic acid metabolism, and glycosylation reactions that sustain cell growth. In metazoans, dihydroorotase is not a standalone enzyme but a domain of the multifunctional CAD protein, which couples it with carbamoyl phosphate synthetase and aspartate transcarbamoylase to form a metabolic complex that channels intermediates efficiently. Because rapidly proliferating cancer cells depend heavily on de novo pyrimidine synthesis, dihydroorotase activity has emerged as a therapeutic node in oncology and a target in antiparasitic drug discovery. Understanding its mechanism, regulation, and disease links is therefore critical for researchers in cancer metabolism, virology, and parasitology.
dihydroorotase activity At A Glance
| GO ID | GO:0004151 |
|---|---|
| GO term | dihydroorotase activity |
| Ontology | molecular_function |
| Synonym | carbamoylaspartic dehydrase activity; DHOase activity; dihydroorotate hydrolase activity; (S)-dihydroorotate amidohydrolase activity |
| Major function | Catalysis of (S)-dihydroorotate + H2O = N-carbamoyl-L-aspartate + H+ |
| Pathway context | De novo pyrimidine biosynthesis |
| Human gene | CAD (carbamoyl-phosphate synthetase 2, aspartate transcarbamoylase, dihydroorotase) |
| Subcellular context | Cytosolic multifunctional enzyme complex in metazoans |
| Representative inhibitor | Orotate analogs that inhibit dihydroorotase and dihydroorotate dehydrogenase |
What Is GO:0004151?
Dihydroorotase activity (GO:0004151) is the catalytic function that converts (S)-dihydroorotate and water into N-carbamoyl-L-aspartate and a proton. It is a hydrolytic reaction that opens the dihydroorotate ring, and it is the third enzymatic step in the de novo pyrimidine biosynthetic pathway. The activity is also known by synonyms such as carbamoylaspartic dehydrase activity, DHOase activity, dihydroorotate hydrolase activity, and (S)-dihydroorotate amidohydrolase activity.
Why Is dihydroorotase activity Important in Cell Biology?
Dihydroorotase activity is important because it controls a rate-limiting segment of de novo pyrimidine biosynthesis, a pathway that cancer cells and activated immune cells rely on for proliferation and survival. Pharmacological or genetic disruption of this activity limits nucleotide supply, impairs DNA replication, and can sensitize tumors to ferroptosis, a form of iron-dependent cell death. Beyond cancer, dihydroorotase is essential in protozoan parasites such as Plasmodium, where orotate analogs that inhibit the enzyme show antimalarial activity. The enzyme also participates in metabolic reprogramming driven by oncoproteins and oncogenic viruses, linking pyrimidine synthesis to mTORC1 signaling, glycolysis, and immune-microenvironment cross-talk.
• Supplies pyrimidine nucleotides for DNA and RNA synthesis in proliferating cells.
• Supports cancer cell proliferation and ferroptosis defence through CAD-dependent pyrimidine synthesis.
• Is a metabolic vulnerability in tumors with high de novo nucleotide demand.
• Is stimulated by oncoproteins such as PFKFB3 and HUWE1 that activate CAD.
• Is hijacked by oncogenic herpesviruses to fuel nucleotide biosynthesis.
• Contributes to hepatocellular carcinoma metastasis via a DHO/UBE4B/NF-kB axis.
• Is a validated antiparasitic target; orotate analogs inhibit dihydroorotase and DHODH.
• Provides a structural model for understanding metalloenzyme catalysis and inhibitor design.
Molecular Mechanism of dihydroorotase activity
Substrate binding and ring-opening hydrolysis
In simple terms: The enzyme grabs a ring-shaped molecule and breaks it open using water.
Dihydroorotase binds (S)-dihydroorotate, the product of the preceding aspartate transcarbamoylase step, and catalyzes its hydrolysis to N-carbamoyl-L-aspartate. This reversible reaction is the third step of de novo pyrimidine biosynthesis and is carried out within the multifunctional CAD complex in metazoans, which channels substrates between active sites.
Multifunctional CAD complex architecture
In simple terms: In humans, the enzyme is part of a three-in-one protein machine.
In humans, dihydroorotase activity is embedded in the CAD protein, which also contains carbamoyl phosphate synthetase and aspartate transcarbamoylase domains. This organization allows efficient substrate channeling and coordination of the first three steps of pyrimidine synthesis, and CAD assembly into higher-order complexes supports cancer cell proliferation and ferroptosis defence.
Metal-dependent catalytic mechanism
In simple terms: The enzyme uses metal ions to activate water for the chemical reaction.
Structural studies of Methanococcus jannaschii dihydroorotase provide a crystal structure of the enzyme, revealing the fold and active-site architecture that supports its hydrolytic mechanism. This structural information helps explain how the enzyme binds dihydroorotate and positions water for nucleophilic attack, and it informs inhibitor design.
Regulation by upstream signaling and oncoproteins
In simple terms: Growth signals tell the enzyme to work faster.
Dihydroorotase flux is regulated indirectly through phosphorylation and activation of CAD by upstream signals. PFKFB3 activates CAD to enhance de novo pyrimidine synthesis for cell growth, and HUWE1 stimulates mTORC1 activity by enhancing Rheb interaction with mTORC1, thereby supporting de novo pyrimidine synthesis. Oncogenic herpesviruses also hijack nucleotide biosynthesis and deamidation-mediated glycolysis, increasing pyrimidine pathway flux.
Pathological rewiring in cancer
In simple terms: In tumors, this enzyme can be rewired to help cancer spread.
In hepatocellular carcinoma, CAD manipulates a tumor-intrinsic DHO/UBE4B/NF-kB pathway and fuels macrophage cross-talk, promoting metastasis. This illustrates how dihydroorotase activity can be integrated into oncogenic signaling networks beyond simple nucleotide supply, and it highlights the enzyme as a potential therapeutic target.
Key Genes Involved in GO:0004151 dihydroorotase activity
The following genes and proteins are directly or functionally linked to dihydroorotase activity (GO:0004151) and its pathway context.
| Gene | Major Role | Research Relevance |
|---|---|---|
| CAD | Multifunctional enzyme containing dihydroorotase activity; catalyzes first three steps of de novo pyrimidine synthesis | Central to cancer metabolism and ferroptosis defence studies |
| DHODH | Dihydroorotate dehydrogenase; catalyzes the fourth step of pyrimidine synthesis downstream of dihydroorotase | Target of orotate analogs and metabolic inhibitors |
| PFKFB3 | Activates CAD to enhance de novo pyrimidine synthesis | Links glycolysis to pyrimidine synthesis in cancer |
| HUWE1 | Stimulates mTORC1 activity and supports de novo pyrimidine synthesis | Connects ubiquitin signaling to nucleotide synthesis |
| UBE4B | Part of the DHO/UBE4B/NF-kB pathway manipulated by CAD in HCC | Implicated in hepatocellular carcinoma metastasis |
| NF-kB | Transcription factor downstream of CAD-driven pathway in HCC | Mediates tumor-macrophage cross-talk |
| mTORC1 | Signaling complex that promotes pyrimidine synthesis | Upstream regulator of CAD-dependent flux |
| Rheb | Activator of mTORC1; enhanced by HUWE1 | Links growth signaling to pyrimidine synthesis |
| ATCase | Aspartate transcarbamoylase domain of CAD; produces dihydroorotate | Provides substrate for dihydroorotase |
| CPSase | Carbamoyl phosphate synthetase domain of CAD; first step of pyrimidine synthesis | Initiates pathway flux |
| DHOase | Dihydroorotase domain of CAD; the activity of GO:0004151 | Direct enzymatic target |
| Methanococcus jannaschii DHOase | Model enzyme for structural studies | Crystal structure informs mechanism and inhibitor design |
| Plasmodium DHOase | Parasite dihydroorotase | Antimalarial drug target |
| Orotate analogs | Small-molecule inhibitors of dihydroorotase and DHODH | Antimalarial activity |
| Ferroptosis regulators | Pathway components affected by pyrimidine synthesis | Link dihydroorotase flux to cell death |
| Macropinocytosis machinery | Nutrient acquisition pathway in cancer | Interacts with metabolic reprogramming |
How Is dihydroorotase activity Regulated?
Dihydroorotase activity is regulated indirectly through the phosphorylation and activation of the multifunctional CAD protein by growth-signaling pathways. mTORC1 signaling, stimulated by HUWE1 via enhanced Rheb interaction, supports de novo pyrimidine synthesis. PFKFB3 activates CAD to enhance de novo pyrimidine synthesis for cell growth. Oncogenic herpesviruses hijack nucleotide biosynthesis and deamidation-mediated glycolysis, increasing pathway flux. In hepatocellular carcinoma, CAD manipulates a DHO/UBE4B/NF-kB pathway that fuels macrophage cross-talk. These layers of regulation allow cells to match pyrimidine supply with proliferative demand and stress conditions such as ferroptosis.
dihydroorotase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| CAD | Cancer proliferation and ferroptosis defence | CAD knockout cancer cell lines with pyrimidine rescue |
| CAD | Hepatocellular carcinoma metastasis | HCC xenograft models with CAD knockdown |
| PFKFB3 | Cancer growth via pyrimidine synthesis | PFKFB3 overexpression and knockout cells |
| HUWE1 | mTORC1-driven pyrimidine synthesis | HUWE1 knockout cells with mTORC1 readouts |
| Parasite DHOase | Malaria | Plasmodium dihydroorotase inhibition assays |
Cancer metabolism and ferroptosis defence
De novo pyrimidine biosynthetic complexes, including CAD-dependent dihydroorotase activity, support cancer cell proliferation and ferroptosis defence. Cancer cells rely on macropinocytosis and metabolic reprogramming to acquire nutrients, and targeting these pathways is a therapeutic strategy. PFKFB3 activation of CAD enhances pyrimidine synthesis for growth, and HUWE1 supports de novo pyrimidine synthesis through mTORC1.
Hepatocellular carcinoma metastasis
CAD manipulates a tumor-intrinsic DHO/UBE4B/NF-kB pathway and fuels macrophage cross-talk, promoting hepatocellular carcinoma metastasis. This links dihydroorotase activity to tumor microenvironment interactions and metastatic progression.
Viral oncogenesis and metabolic hijacking
Oncogenic herpesviruses hijack nucleotide biosynthesis and deamidation-mediated glycolysis, increasing pyrimidine pathway flux that includes dihydroorotase activity. This illustrates how viral oncoproteins can rewire host metabolism to support viral replication and transformation.
Parasitic infections and antimalarial drug discovery
Orotate analogs that inhibit dihydroorotase and dihydroorotate dehydrogenase show antimalarial activity, validating the parasite pyrimidine pathway as a drug target. Structural studies of dihydroorotase from Methanococcus jannaschii provide a framework for understanding inhibitor binding.
From dihydroorotase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of dihydroorotase activity impair proliferation? | CAD knockout cell lines with or without pyrimidine supplementation |
| Does a point mutation in the catalytic site abolish enzyme activity? | Point-mutation knock-in of CAD active-site residues |
| Can tagged dihydroorotase be used for interaction studies? | Tagged knock-in of CAD for affinity purification |
| Does overexpression of CAD drive pyrimidine flux? | CAD overexpression cell lines |
| Does PFKFB3 regulate CAD-dependent pyrimidine synthesis? | PFKFB3 knockout and overexpression models |
| Does HUWE1 support de novo pyrimidine synthesis? | HUWE1 knockout with mTORC1 and pyrimidine flux assays |
How to Study the dihydroorotase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Stable isotope tracing | Flux through de novo pyrimidine synthesis | Cancer metabolism studies |
| Enzymatic activity assay | Dihydroorotase catalytic rate | Inhibitor screening |
| CRISPR knockout screen | Gene dependencies for proliferation | Cancer target discovery |
| Affinity purification-mass spectrometry | Protein interactions of CAD | Complex composition studies |
| Phosphoproteomics | CAD phosphorylation status | Signaling regulation |
| X-ray crystallography | Enzyme structure and active site | Mechanism and inhibitor design |
| Cell viability assay | Proliferation and survival | Drug response testing |
Metabolic flux analysis
Stable isotope tracing with labeled precursors can measure flux through de novo pyrimidine biosynthesis, including the dihydroorotase step, in cancer cells and tissues. This approach quantifies how genetic or pharmacological perturbations alter pathway activity.
Enzymatic activity assays
Dihydroorotase activity can be measured in vitro by monitoring the conversion of (S)-dihydroorotate to N-carbamoyl-L-aspartate, and such assays are used to evaluate inhibitors such as orotate analogs. Structural studies of the enzyme inform assay design and inhibitor optimization.
CRISPR-based genetic screens
CRISPR knockout screens targeting CAD and related metabolic genes can identify dependencies on dihydroorotase activity in cancer cell lines and in vivo models. These screens link genotype to proliferation and survival phenotypes.
Proteomics and interaction studies
Affinity purification and mass spectrometry of tagged CAD complexes can reveal interacting proteins and post-translational modifications that regulate dihydroorotase activity. Such studies help map the signaling networks that control pyrimidine synthesis.
How CRISPR Can Be Used to Study GO:0004151 dihydroorotase activity
Knockout
CRISPR knockout of CAD eliminates dihydroorotase activity and impairs de novo pyrimidine synthesis, providing a model to study proliferation defects and ferroptosis sensitivity. Such knockouts can be rescued with exogenous pyrimidines to confirm on-target effects.
Point Mutation
Point mutations in the dihydroorotase active site of CAD can be introduced to dissect catalytic residues and separate enzyme activity from other CAD functions. These models help validate structural predictions and inhibitor binding sites.
Knock-in
Tagged knock-in of CAD allows endogenous labeling of the multifunctional enzyme for interaction and localization studies without overexpression artifacts. This approach supports proteomic and imaging analyses of dihydroorotase-containing complexes.
Overexpression
Overexpression of CAD or its regulators such as PFKFB3 can increase pyrimidine flux and drive proliferation, providing a gain-of-function model to study pathway activation. Overexpression models are useful for testing inhibitors of dihydroorotase activity.
How EDITGENE Supports dihydroorotase activity Research
Researchers studying dihydroorotase activity-related genes often need to determine whether a candidate gene is causally involved in pyrimidine synthesis, cancer proliferation, or drug response. Rigorous causal inference requires well-controlled genetic models that isolate the enzyme activity from confounding pathway effects. EDITGENE provides a comprehensive suite of CRISPR services to generate such models efficiently and reproducibly.
Contact EDITGENE today to design your custom CRISPR model for dihydroorotase activity research.
Frequently Asked Questions About dihydroorotase activity
What is dihydroorotase activity?
Dihydroorotase activity (GO:0004151) is the catalysis of the reaction (S)-dihydroorotate + H2O = N-carbamoyl-L-aspartate + H+, the third step of de novo pyrimidine biosynthesis.
What genes are involved in dihydroorotase activity?
In humans, dihydroorotase activity is carried by the CAD gene, which encodes a multifunctional protein also containing carbamoyl phosphate synthetase and aspartate transcarbamoylase domains.
What is the GO ID for dihydroorotase activity?
The Gene Ontology ID for dihydroorotase activity is GO:0004151, classified under molecular_function.
Why is dihydroorotase activity important in cancer?
It supports de novo pyrimidine synthesis required for cancer cell proliferation and ferroptosis defence, making it a metabolic vulnerability.
How is dihydroorotase activity regulated?
It is regulated indirectly through phosphorylation and activation of CAD by upstream signals such as mTORC1, PFKFB3, and HUWE1.
What diseases are linked to dihydroorotase activity?
Cancer, including hepatocellular carcinoma, and parasitic infections such as malaria are linked to this activity.
Can dihydroorotase be inhibited by drugs?
Yes, orotate analogs inhibit dihydroorotase and dihydroorotate dehydrogenase and show antimalarial activity.
What is the structure of dihydroorotase?
The crystal structure of Methanococcus jannaschii dihydroorotase has been solved, providing insight into its active site and mechanism.
How do CRISPR knockouts help study dihydroorotase activity?
CRISPR knockout of CAD eliminates the activity and allows researchers to measure effects on proliferation, nucleotide pools, and ferroptosis.
What methods measure dihydroorotase activity?
Enzymatic assays, stable isotope tracing, and metabolic flux analysis are commonly used to measure pathway activity.
Conclusion
Dihydroorotase activity (GO:0004151) is a central enzymatic step in de novo pyrimidine biosynthesis, embedded in the multifunctional CAD protein in humans and essential for proliferation and stress responses in cancer cells. Its links to ferroptosis defence, oncogenic signaling, viral metabolic hijacking, and parasite survival make it a compelling target for therapeutic development. Continued research using CRISPR models, metabolic flux analysis, and structural biology will clarify how this activity can be modulated in disease.
References
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- 2. Xu G et al.. 2025. Survival strategies of cancer cells: the role of macropinocytosis in nutrient acquisition, metabolic reprogramming, and therapeutic targeting.. Autophagy 21(4):693-718 PMID: 39817564
- 3. Wan Q et al.. 2024. Hijacking of nucleotide biosynthesis and deamidation-mediated glycolysis by an oncogenic herpesvirus.. Nat Commun 15(1):1442 PMID: 38365882
- 4. Ikeda T et al.. 2025. HUWE1 stimulates mTORC1 activity by enhancing Rheb interaction with mTORC1 and supports de novo pyrimidine synthesis.. Cell Rep 44(10):116382 PMID: 41075246
- 5. Vitali J et al.. 2023. Crystal structure of Methanococcus jannaschii dihydroorotase.. Proteins 91(1):91-98 PMID: 35978488
- 6. Da Q et al.. 2025. PFKFB3 activates CAD to enhance de novo pyrimidine synthesis for cell growth.. Cell Rep 44(8):116071 PMID: 40742808
- 7. Pan J et al.. 2026. CAD manipulates tumor intrinsic DHO/UBE4B/NF-κB pathway and fuels macrophage cross-talk, promoting HCC metastasis.. Hepatology 83(3):451-465 PMID: 40073276
- 8. Krungkrai J et al.. 1992. Antimalarial activity of orotate analogs that inhibit dihydroorotase and dihydroorotate dehydrogenase.. Biochem Pharmacol 43(6):1295-301 PMID: 1348618
