GO:0004088 carbamoyl-phosphate synthase (glutamine-hydrolyzing) activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0004088 describes the glutamine-dependent carbamoyl-phosphate synthase reaction that converts hydrogencarbonate, L-glutamine and 2 ATP into carbamoyl phosphate, L-glutamate, 2 ADP, phosphate and 2 H+.
• In metazoans this activity is typically carried by CAD (carbamoyl-phosphate synthetase 2, aspartate transcarbamoylase, dihydroorotase), the rate-limiting enzyme of de novo pyrimidine biosynthesis.
• The enzyme is strongly upregulated in proliferating tissues and cancer cells, making it a marker and potential target in nucleotide-synthesis research.
• Glutamine availability and glycolytic signaling through PFKFB3 regulate CAD activity and de novo pyrimidine flux.
• Loss of glutamine-dependent carbamoyl-phosphate synthase activity causes hyperammonemia and blocks pyrimidine-dependent DNA synthesis.
• CRISPR knockout, point-mutation, knock-in and overexpression models are essential to dissect CAD/CPS II function in cancer, immunology and metabolic disease.
Description
Carbamoyl-phosphate synthase (glutamine-hydrolyzing) activity, encoded by GO:0004088, is a molecular function that catalyzes the ATP-dependent synthesis of carbamoyl phosphate from hydrogencarbonate and L-glutamine. This reaction is the committed and rate-limiting step of de novo pyrimidine biosynthesis in metazoans, and it also contributes to arginine and urea-cycle nitrogen handling in some organisms. Because rapidly dividing cells require large amounts of pyrimidine nucleotides for DNA and RNA synthesis, this activity is tightly linked to cell proliferation and tumor growth. The enzyme was first recognized as a glutamine-hydrolyzing carbamoyl-phosphate synthetase (CPS II) whose activity increases markedly in cancer cells and in mitogen-stimulated lymphocytes. In mammals, the activity resides in the multifunctional CAD protein, which combines carbamoyl-phosphate synthetase, aspartate transcarbamoylase and dihydroorotase activities on a single polypeptide. Understanding GO:0004088 therefore matters for cancer metabolism, immunometabolism, nitrogen homeostasis and antiparasitic drug discovery. Recent work shows that CAD is activated by glycolytic signaling through PFKFB3 and that pyrimidine synthesis pathway choice is cell-state specific, underscoring the need for precise genetic models. This article summarizes the definition, mechanism, key genes, disease links and research methods for GO:0004088.
carbamoyl-phosphate synthase (glutamine-hydrolyzing) activity At A Glance
| GO ID | GO:0004088 |
|---|---|
| GO term | carbamoyl-phosphate synthase (glutamine-hydrolyzing) activity |
| Ontology | molecular_function |
| Synonym | carbamoyl phosphate synthetase II activity; glutamine-dependent carbamoyl-phosphate synthase activity; CPS activity; GD-CPSase activity |
| Major function | Catalyzes the ATP-dependent formation of carbamoyl phosphate from hydrogencarbonate and L-glutamine, the first committed step of de novo pyrimidine biosynthesis |
| Reaction | hydrogencarbonate + L-glutamine + 2 ATP + H2O = carbamoyl phosphate + L-glutamate + 2 ADP + phosphate + 2 H+ |
| Cofactors | Mg2+ or Mn2+ required for ATP-dependent phosphorylation steps |
| Subcellular context | Cytosolic in metazoans as part of the CAD multifunctional protein |
| Representative genes | CAD (human), pyr-1/pyrAB (microbes), CPS II in Toxoplasma gondii |
What Is GO:0004088?
GO:0004088 is defined as the catalysis of the reaction: hydrogencarbonate + L-glutamine + 2 ATP + H2O = carbamoyl phosphate + L-glutamate + 2 ADP + phosphate + 2 H+. In other words, the enzyme uses the amide nitrogen of glutamine, bicarbonate and the energy of two ATP molecules to build carbamoyl phosphate, releasing glutamate, ADP, phosphate and protons. This is the glutamine-dependent isoform of carbamoyl-phosphate synthase, often called CPS II or CAD in animals, and it is distinct from the ammonia-dependent mitochondrial CPS I of the urea cycle.
Why Is carbamoyl-phosphate synthase (glutamine-hydrolyzing) activity Important in Cell Biology?
GO:0004088 is important because it gates the flux of de novo pyrimidine biosynthesis, a pathway that supplies the CTP, UTP and thymidine nucleotides needed for DNA replication and RNA synthesis. Its activity is elevated in cancer cells and in normal proliferating tissues, and it is regulated by glutamine availability and oncogenic signaling, making it a central node in cancer metabolism and immunometabolism. Defects in the pathway cause hyperammonemia and impair nucleotide supply, while in parasites such as Toxoplasma gondii the enzyme is a potential drug target. Consequently, researchers use GO:0004088 as an anchor for studying proliferation, nitrogen metabolism, metabolic reprogramming and therapeutic vulnerabilities.
• Rate-limiting step of de novo pyrimidine biosynthesis, controlling nucleotide supply for DNA and RNA synthesis.
• Activity is markedly increased in cancer cells and in mitogen-stimulated lymphocytes, linking it to proliferation.
• Regulated by glutamine concentration, connecting amino-acid availability to nucleotide synthesis.
• Activated downstream of glycolytic signaling via PFKFB3, integrating glucose metabolism with pyrimidine synthesis.
• Loss of function causes hyperammonemia and blocks pyrimidine-dependent DNA synthesis.
• Cell-state-specific pyrimidine pathway choice makes it relevant to differentiation and immune cell states.
• Enzyme from Toxoplasma gondii is a validated antiparasitic target candidate.
• Provides a biomarker and therapeutic target in cancers with high pyrimidine demand.
• Enables metabolic flux studies using 13C/15N labeling and CRISPR models.
• Supports research on urea-cycle nitrogen handling and arginine metabolism in relevant organisms.
What Happens During carbamoyl-phosphate synthase (glutamine-hydrolyzing) activity?
Substrate binding and bicarbonate activation
In simple terms: The enzyme first grabs bicarbonate and activates it using ATP.
The reaction begins with binding of hydrogencarbonate and ATP at the synthetase active site, where ATP phosphorylates bicarbonate to form a reactive carboxyphosphate intermediate. This step requires divalent cations such as Mg2+ or Mn2+ and is the first of two ATP-consuming events in the overall reaction. The glutamine-hydrolyzing enzyme uses bicarbonate rather than free ammonia, distinguishing it from the mitochondrial urea-cycle CPS I.
Glutamine hydrolysis and ammonia transfer
In simple terms: The enzyme breaks down glutamine to deliver nitrogen for the reaction.
In the second stage, L-glutamine binds at a separate glutaminase domain and is hydrolyzed to glutamate plus ammonia, which is channeled to the synthetase site. This intramolecular channeling prevents loss of ammonia and is a hallmark of glutamine-dependent amidotransferases. Glutamine concentration directly influences the reaction rate, as shown in lymphocytes where glutamine availability modulates CPS II activity and DNA synthesis.
Carbamoyl phosphate formation and product release
In simple terms: The enzyme combines the activated bicarbonate with nitrogen to make carbamoyl phosphate.
The carboxyphosphate intermediate reacts with the channeled ammonia to form carbamate, which is then phosphorylated by a second ATP to yield carbamoyl phosphate. The products carbamoyl phosphate, L-glutamate, 2 ADP, phosphate and 2 H+ are released, and carbamoyl phosphate feeds directly into the pyrimidine pathway via aspartate transcarbamoylase. In CAD, this activity is physically coupled to the downstream aspartate transcarbamoylase and dihydroorotase domains, enabling substrate channeling.
Coupling to de novo pyrimidine biosynthesis
In simple terms: The carbamoyl phosphate made here becomes the building block for pyrimidine nucleotides.
Carbamoyl phosphate produced by GO:0004088 is condensed with aspartate to form carbamoyl aspartate, the committed step of pyrimidine ring assembly. This flux supports DNA replication and is elevated in proliferating cells and tumors. Recent work shows that PFKFB3 activates CAD to enhance de novo pyrimidine synthesis for cell growth, directly linking glycolytic signaling to this activity.
Regulation by substrates and signaling
In simple terms: The enzyme's speed is tuned by glutamine levels and growth signals.
CPS II activity responds to glutamine concentration, and glutamine restriction reduces both enzyme activity and DNA synthesis in stimulated lymphocytes. In cancer cells, the activity is elevated and subject to regulation by oncogenic and metabolic signals. Cell-state-specific pyrimidine synthesis pathway choice further indicates that this activity is context-dependent.
Key Genes Involved in GO:0004088 carbamoyl-phosphate synthase (glutamine-hydrolyzing) activity
The genes and proteins below represent the main enzymes, regulators and pathway components associated with GO:0004088 across human, microbial and parasite systems.
| Gene | Major Role | Research Relevance |
|---|---|---|
| CAD | Multifunctional enzyme carrying carbamoyl-phosphate synthetase, aspartate transcarbamoylase and dihydroorotase activities in metazoans | Central to de novo pyrimidine synthesis and cancer metabolism studies |
| CPS1 | Mitochondrial ammonia-dependent carbamoyl-phosphate synthetase of the urea cycle | Contrasts with glutamine-dependent GO:0004088 and informs nitrogen handling |
| PFKFB3 | Glycolytic enzyme that activates CAD | Links glycolysis to pyrimidine synthesis and cell growth |
| pyrAB | Microbial glutamine-dependent carbamoyl-phosphate synthetase | Model for enzyme structure and mechanism |
| pyr-1 | Fungal/parasite glutamine-dependent CPS II | Genetic model for pathway dissection |
| TgCPSII | Toxoplasma gondii glutamine-dependent CPS II | Antiparasitic drug target candidate |
| GLS | Glutaminase supplying glutamate/ammonia for nitrogen metabolism | Modulates glutamine-dependent flux |
| ASS1 | Argininosuccinate synthetase consuming carbamoyl phosphate pathway products | Connects pyrimidine and arginine metabolism |
| OTC | Ornithine transcarbamoylase of the urea cycle | Context for nitrogen disposal and hyperammonemia |
| UMPS | UMP synthase downstream of carbamoyl phosphate | Pyrimidine pathway readout |
| CTPS1 | CTP synthase consuming UTP | Downstream nucleotide demand marker |
| DHODH | Dihydroorotate dehydrogenase downstream of CAD | Target and pathway flux indicator |
| mTOR | Growth signaling kinase influencing nucleotide synthesis | Regulation of proliferation-linked flux |
| MYC | Oncogene driving nucleotide synthesis programs | Cancer metabolism context |
| ATF4 | Stress-responsive transcription factor linked to amino-acid metabolism | Integration of nitrogen stress |
| GCN2 | Amino-acid sensor kinase | Glutamine-dependent stress responses |
| SLC1A5 | Glutamine transporter | Controls substrate availability for GO:0004088 |
| PPAT | Phosphoribosyl pyrophosphate amidotransferase | Parallel nucleotide synthesis pathway comparison |
How Is carbamoyl-phosphate synthase (glutamine-hydrolyzing) activity Regulated?
GO:0004088 is regulated at multiple levels. Substrate availability, especially glutamine concentration, directly modulates enzyme activity, as shown in mitogen-stimulated lymphocytes where glutamine levels affect CPS II activity and DNA synthesis. Glycolytic signaling through PFKFB3 activates CAD to enhance de novo pyrimidine synthesis, linking glucose metabolism to this activity. The enzyme is also subject to regulation during proliferation, with increased activity in cancer cells and normal proliferating tissues. Cell-state-specific pyrimidine synthesis pathway choice indicates that additional context-dependent regulators exist. Growth-factor and nutrient-sensing pathways such as mTOR and amino-acid stress responses further shape nucleotide synthesis flux.
carbamoyl-phosphate synthase (glutamine-hydrolyzing) activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| CAD | Cancer proliferation and pyrimidine dependency | CAD knockout and overexpression cancer cell lines |
| CPS1 | Hyperammonemia and urea-cycle disorders | Patient-derived hepatocyte models and point-mutation knock-in |
| TgCPSII | Toxoplasma gondii infection | Parasite knockout and enzyme inhibition assays |
| GLS | Glutamine-dependent tumor growth | GLS knockout and glutamine restriction models |
| PFKFB3 | Glycolysis-driven pyrimidine synthesis in cancer | PFKFB3 knockout and CAD activation studies |
Cancer metabolism and proliferation
Carbamoyl-phosphate synthase (glutamine-hydrolyzing) activity is increased in cancer cells, supporting the high pyrimidine demand of rapid proliferation. CAD, which carries this activity, is activated by PFKFB3 to enhance de novo pyrimidine synthesis for cell growth. These findings make GO:0004088 a candidate biomarker and therapeutic target in tumors with elevated nucleotide synthesis.
Hyperammonemia and nitrogen metabolism disorders
Impairment of carbamoyl-phosphate synthetase function contributes to hyperammonemic states, as illustrated by valproate-induced hyperammonemic encephalopathy. Because the glutamine-hydrolyzing enzyme participates in nitrogen handling, its dysfunction can disturb ammonia detoxification and amino-acid balance. This links GO:0004088 to neurological complications of metabolic origin.
Immunometabolism and lymphocyte proliferation
In mitogen-stimulated lymphocytes, CPS II activity depends on glutamine concentration and correlates with DNA synthesis, tying GO:0004088 to immune cell proliferation. This makes the activity relevant to autoimmune and inflammatory conditions where lymphocyte expansion occurs. Cell-state-specific pyrimidine pathway choice further suggests context-dependent roles in immune cells.
Parasitic infections and antiparasitic targets
Glutamine-dependent carbamoyl-phosphate synthetase II from Toxoplasma gondii has been characterized as a potential drug target, since the parasite relies on de novo pyrimidine synthesis. The organization and sequence of the parasite enzyme differ from host enzymes, offering selectivity opportunities. Thus GO:0004088 is relevant to infectious disease research.
From carbamoyl-phosphate synthase (glutamine-hydrolyzing) activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Is CAD required for proliferation? | CRISPR knockout of CAD in cancer cell lines |
| Does a point mutation alter catalytic activity? | Point-mutation knock-in of CAD active-site residues |
| How does a tag affect localization? | Tagged knock-in of CAD with fluorescent or affinity tag |
| Does overexpression increase pyrimidine flux? | CAD overexpression in cell lines with metabolic labeling |
| Which genes modify the phenotype? | CRISPR library screening in CAD-mutant backgrounds |
| How does glutamine availability affect activity? | Glutamine titration in wild-type and mutant cells |
How to Study the carbamoyl-phosphate synthase (glutamine-hydrolyzing) activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Enzymatic activity assay | Carbamoyl phosphate production rate | Comparing normal and cancer cells |
| 13C/15N metabolic labeling | De novo pyrimidine flux | Cell-state pathway choice |
| RNA-seq | CAD and pathway gene expression | Proliferation and cancer profiling |
| Proteomics | Protein abundance and modifications | Regulatory network mapping |
| CRISPR knockout | Loss-of-function phenotype | Causal gene testing |
| Glutamine titration | Substrate dependence of activity | Immunometabolism studies |
| Ammonia measurement | Nitrogen handling capacity | Hyperammonemia models |
| Parasite enzyme assay | TgCPSII inhibition | Antiparasitic drug screening |
Enzymatic activity assays
Direct measurement of carbamoyl-phosphate synthase activity using radiolabeled bicarbonate or coupled assays remains the gold standard for GO:0004088. These assays quantify product formation and are used to compare normal and proliferating tissues. They can be combined with glutamine titration to assess substrate dependence.
Metabolic flux analysis
Stable-isotope labeling with 13C-glutamine or 15N tracers allows measurement of de novo pyrimidine flux through the CAD pathway. This approach reveals cell-state-specific pathway choice and the contribution of GO:0004088 to nucleotide pools. It is often paired with mass spectrometry of nucleotide intermediates.
Transcriptomic and proteomic profiling
RNA-seq and proteomics can quantify CAD expression and identify co-regulated genes in proliferation programs. These methods help define the regulatory network around GO:0004088. They are useful for comparing cancer versus normal tissues.
Genetic perturbation and phenotyping
CRISPR knockout, knockdown and overexpression of CAD or parasite CPS II enable causal testing of GO:0004088 function. Phenotypes such as proliferation, DNA synthesis and ammonia handling are then measured. These models are essential for target validation.
How CRISPR Can Be Used to Study GO:0004088 carbamoyl-phosphate synthase (glutamine-hydrolyzing) activity
Knockout
CRISPR knockout of CAD or parasite CPS II genes abolishes GO:0004088 activity and reveals its requirement for proliferation and nucleotide supply. Knockout models are used to test whether cells become dependent on exogenous pyrimidines. They also help validate the enzyme as a therapeutic target.
Point Mutation
Point-mutation knock-in of active-site residues can dissect the catalytic steps of GO:0004088, including ATP binding and glutamine hydrolysis. Such models distinguish catalytic from structural functions. They are valuable for understanding enzyme mechanism and drug resistance.
Knock-in
Tagged knock-in of CAD allows visualization of localization and interaction partners in living cells. Knock-in of reporter or affinity tags supports proteomic and imaging studies of GO:0004088. This approach preserves endogenous regulation.
Overexpression
Overexpression of CAD or CPS II increases flux through GO:0004088 and can drive pyrimidine-dependent growth. Overexpression models are used to test sufficiency and to identify metabolic bottlenecks. They complement knockout studies for bidirectional causal inference.
How EDITGENE Supports carbamoyl-phosphate synthase (glutamine-hydrolyzing) activity Research
Researchers studying carbamoyl-phosphate synthase (glutamine-hydrolyzing) activity-related genes often need to determine whether a candidate gene is causally involved in pyrimidine synthesis, proliferation or nitrogen metabolism. EDITGENE provides publication-ready CRISPR cell models and screening services to answer these questions with rigor and reproducibility.
Contact EDITGENE today to design your custom CRISPR model for carbamoyl-phosphate synthase (glutamine-hydrolyzing) activity research.
Frequently Asked Questions About carbamoyl-phosphate synthase (glutamine-hydrolyzing) activity
What is carbamoyl-phosphate synthase (glutamine-hydrolyzing) activity?
It is the enzymatic activity defined by GO:0004088 that converts hydrogencarbonate, L-glutamine and 2 ATP into carbamoyl phosphate, L-glutamate, 2 ADP, phosphate and 2 H+, the first step of de novo pyrimidine synthesis.
What genes are involved in carbamoyl-phosphate synthase (glutamine-hydrolyzing) activity?
In humans the activity resides in CAD; other relevant genes include CPS1, PFKFB3, pyrAB, pyr-1 and TgCPSII in parasites.
Why is carbamoyl-phosphate synthase activity important in cancer?
Cancer cells show increased activity to support high pyrimidine demand during proliferation, and CAD is activated by PFKFB3 to enhance de novo pyrimidine synthesis.
How is carbamoyl-phosphate synthase activity regulated?
It is regulated by glutamine availability, glycolytic signaling through PFKFB3, and proliferation-associated programs.
What reaction does GO:0004088 catalyze?
The reaction hydrogencarbonate + L-glutamine + 2 ATP + H2O = carbamoyl phosphate + L-glutamate + 2 ADP + phosphate + 2 H+.
Is carbamoyl-phosphate synthase the same as CPS I?
No, GO:0004088 is the glutamine-dependent CPS II/CAD activity, distinct from the ammonia-dependent mitochondrial CPS I of the urea cycle.
What diseases are linked to this activity?
Cancer proliferation, hyperammonemic encephalopathy, immunometabolic disorders and parasitic infections have been linked to this activity.
How can I study carbamoyl-phosphate synthase activity in the lab?
Enzymatic assays, 13C/15N metabolic labeling, RNA-seq, proteomics and CRISPR knockout or overexpression models are commonly used.
Does glutamine concentration affect this enzyme?
Yes, glutamine concentration directly affects CPS II activity and DNA synthesis in stimulated lymphocytes.
What CRISPR models are available for GO:0004088 research?
Knockout, point-mutation, knock-in, tagged knock-in and overexpression models can be generated for CAD and related genes.
Conclusion
GO:0004088, carbamoyl-phosphate synthase (glutamine-hydrolyzing) activity, is a central metabolic function that gates de novo pyrimidine biosynthesis and connects glutamine, glucose and nucleotide metabolism. Its dysregulation is implicated in cancer, hyperammonemia and parasitic infections, making it a valuable target for mechanistic and therapeutic research. CRISPR-based knockout, point-mutation, knock-in and overexpression models, combined with metabolic and omics methods, provide the tools needed to dissect this activity in health and disease.
References
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- 2. Da Q et al.. 2025. PFKFB3 activates CAD to enhance de novo pyrimidine synthesis for cell growth.. Cell Rep 44(8):116071 PMID: 40742808
- 3. Segura-Bruna N et al.. 2006. Valproate-induced hyperammonemic encephalopathy.. Acta Neurol Scand 114(1):1-7 PMID: 16774619
- 4. Szondy Z et al.. 1989. The effect of glutamine concentration on the activity of carbamoyl-phosphate synthase II and on the incorporation of [3H]thymidine into DNA in rat mesenteric lymphocytes stimulated by phytohaemagglutinin.. Biochem J 261(3):979-83 PMID: 2803258
- 5. Savani MR et al.. 2026. Nitrogen metabolism profiling reveals cell state-specific pyrimidine synthesis pathway choice.. Nat Metab 8(5):1124-1148 PMID: 42056505
- 6. Aoki T et al.. 1982. Regulatory properties and behavior of activity of carbamoyl phosphate synthetase II (glutamine-hydrolyzing) in normal and proliferating tissues.. J Biol Chem 257(1):432-8 PMID: 7053379
- 7. Fox BA et al.. 2003. Organisation and sequence determination of glutamine-dependent carbamoyl phosphate synthetase II in Toxoplasma gondii.. Int J Parasitol 33(1):89-96 PMID: 12547350
- 8. Weber G et al.. 1986. Regulation of carbamoyl-phosphate synthase II.. Adv Enzyme Regul 25:65-83 PMID: 3544709
