GO:0004087 carbamoyl-phosphate synthase (ammonia) activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0004087 describes the ammonia-dependent carbamoyl-phosphate synthase (CPS1) reaction that converts 2 ATP, bicarbonate and ammonium into carbamoyl phosphate, 2 ADP, phosphate and 2 protons.
• CPS1 is the rate-limiting mitochondrial enzyme of the urea cycle and is essential for ammonia detoxification and pyrimidine synthesis.
• CPS1 activity is controlled by intramitochondrial citrate and by N-acetylglutamate, linking fuel availability to ureagenesis.
• Loss of CPS1 rewires metabolism, reducing aspartate and promoting hepatocellular carcinoma metastasis.
• CPS1 is post-translationally modified by SIRT5-mediated desuccinylation, which can affect its enzymatic function.
• Dysregulated CPS1 and urea cycle flux are observed in non-alcoholic fatty liver disease and in p53-dependent tumour metabolism.
Description
Carbamoyl-phosphate synthase (ammonia) activity, encoded by GO:0004087, is a mitochondrial molecular function that catalyzes the ATP-dependent synthesis of carbamoyl phosphate from ammonia, bicarbonate and two molecules of ATP. This reaction is the first and rate-limiting step of the urea cycle, and it is also a critical entry point for pyrimidine biosynthesis in proliferating cells. Because it directly consumes ammonia and bicarbonate, CPS1 sits at the intersection of nitrogen disposal, acid-base balance and nucleotide metabolism. Researchers study GO:0004087 to understand how cells handle nitrogen stress, how metabolic reprogramming supports tumour growth, and how inherited or acquired defects in ureagenesis contribute to liver disease. The enzyme is also a target for understanding mitochondrial energy coupling, since its activity depends on ATP and is modulated by intramitochondrial citrate and N-acetylglutamate. In this article we summarize the authoritative QuickGO definition, the catalytic and regulatory mechanisms, the key genes and proteins involved, and the experimental models and methods used to investigate this activity.
carbamoyl-phosphate synthase (ammonia) activity At A Glance
| GO ID | GO:0004087 |
|---|---|
| GO term | carbamoyl-phosphate synthase (ammonia) activity |
| Ontology | molecular_function |
| Synonym | CPS I activity; carbamoylphosphate synthase activity; carbamoyl-phosphate synthetase I activity; carbon-dioxide:ammonia ligase (ADP-forming, carbamate-phosphorylating) |
| Major function | Catalyzes the ATP-dependent formation of carbamoyl phosphate from ammonia and bicarbonate, the first committed step of the urea cycle and a key anaplerotic reaction for pyrimidine synthesis. |
| Reaction | 2 ATP + hydrogencarbonate + NH4+ = 2 ADP + carbamoyl phosphate + 2 H+ + phosphate |
| Cofactors | Mg2+ or Mn2+ required for ATP binding and catalysis; N-acetylglutamate acts as an essential allosteric activator. |
| Subcellular location | Mitochondrial matrix |
| Representative gene | CPS1 (human), Cps1 (mouse/rat) |
What Is GO:0004087?
GO:0004087, carbamoyl-phosphate synthase (ammonia) activity, is defined as the catalysis of the reaction: 2 ATP + hydrogencarbonate + NH4+ = 2 ADP + carbamoyl phosphate + 2 H+ + phosphate. In other words, the enzyme uses the energy of ATP hydrolysis to ligate ammonia and bicarbonate into carbamoyl phosphate, releasing ADP, inorganic phosphate and protons. This activity is synonymous with CPS I activity, carbamoylphosphate synthetase (ammonia) activity, and carbon-dioxide:ammonia ligase (ADP-forming, carbamate-phosphorylating). It is a molecular_function term in the Gene Ontology and is distinct from the glutamine-dependent CPS II (which uses glutamine rather than ammonia) and from other carbamoyltransferases.
Why Is carbamoyl-phosphate synthase (ammonia) activity Important in Cell Biology?
GO:0004087 is central to nitrogen homeostasis and to the metabolic reprogramming seen in cancer and liver disease. The reaction it describes removes toxic ammonia and produces carbamoyl phosphate, which is used both for urea synthesis and for de novo pyrimidine biosynthesis. In KRAS/LKB1-mutant lung cancer, CPS1 maintains pyrimidine pools and DNA synthesis, making it a potential metabolic vulnerability. In hepatocellular carcinoma, loss of CPS1 reduces aspartate levels and potentiates metastasis. CPS1 is also regulated by p53 to control ammonia metabolism and polyamine biosynthesis, linking this enzymatic activity to tumour suppressor function. In non-alcoholic fatty liver disease, urea cycle dysregulation including altered CPS1 expression contributes to hyperammonaemia and disease progression. Understanding CPS1 activity is therefore essential for developing therapies that target nitrogen metabolism, nucleotide supply and mitochondrial energy balance.
• Rate-limiting enzyme of the urea cycle and primary route for ammonia detoxification in the liver.
• Supplies carbamoyl phosphate for de novo pyrimidine synthesis, supporting DNA replication in proliferating cells.
• Loss of CPS1 reduces aspartate and promotes metastasis in hepatocellular carcinoma.
• p53 regulates CPS1 to control ammonia metabolism and polyamine biosynthesis, linking urea cycle to tumour suppression.
• CPS1 activity is modulated by intramitochondrial citrate and N-acetylglutamate, integrating fuel availability with ureagenesis.
• SIRT5-mediated desuccinylation of CPS1 can alter its enzymatic activity, connecting mitochondrial sirtuins to nitrogen metabolism.
• Urea cycle dysregulation, including CPS1 changes, is observed in non-alcoholic fatty liver disease.
• CPS1 is a potential therapeutic target in cancers with high pyrimidine demand, such as KRAS/LKB1-mutant lung cancer.
• The enzyme is a model system for studying ATP-dependent ligation and allosteric regulation in mitochondria.
• CPS1 deficiency causes hyperammonaemia, and its study informs inherited metabolic disorders.
What Happens During carbamoyl-phosphate synthase (ammonia) activity?
Substrate binding and activation
In simple terms: The enzyme first grabs its raw materials: ammonia, bicarbonate and ATP.
CPS1 binds ammonium, bicarbonate and two molecules of ATP in an ordered manner. The reaction requires free ammonia (NH4+) rather than glutamine, distinguishing it from CPS II. N-acetylglutamate is an essential allosteric activator that induces conformational changes necessary for catalysis. Intramitochondrial citrate also modulates CPS1 activity, linking the enzyme to the tricarboxylic acid cycle and energy status.
ATP-dependent phosphorylation and carbamate formation
In simple terms: ATP provides energy to combine ammonia and bicarbonate into an unstable intermediate.
The first ATP molecule phosphorylates bicarbonate to form carboxyphosphate, which then reacts with ammonia to produce carbamate. This step consumes one ATP and releases ADP and inorganic phosphate. The reaction is highly regulated because it commits nitrogen to the urea cycle and to pyrimidine synthesis.
Second ATP-dependent phosphorylation to carbamoyl phosphate
In simple terms: A second ATP is used to add a phosphate group to carbamate, making carbamoyl phosphate.
The second ATP phosphorylates carbamate to form carbamoyl phosphate, the final product of the reaction. This step also releases ADP and a proton. The overall reaction produces carbamoyl phosphate, which is then used by ornithine transcarbamylase in the urea cycle or by aspartate transcarbamylase in pyrimidine biosynthesis.
Coupling to urea cycle and pyrimidine synthesis
In simple terms: The product is a building block for both waste disposal and DNA/RNA synthesis.
Carbamoyl phosphate generated by CPS1 is channeled into the urea cycle for ammonia detoxification and into de novo pyrimidine synthesis for nucleotide production. In KRAS/LKB1-mutant lung cancer, CPS1 activity maintains pyrimidine pools and supports DNA synthesis, highlighting its role in proliferation. In hepatocellular carcinoma, loss of CPS1 reduces aspartate levels and promotes metastasis, indicating a broader metabolic role.
Key Genes Involved in GO:0004087 carbamoyl-phosphate synthase (ammonia) activity
The following genes and proteins are directly or functionally linked to carbamoyl-phosphate synthase (ammonia) activity and its metabolic context.
| Gene | Major Role | Research Relevance |
|---|---|---|
| CPS1 | Encodes the mitochondrial enzyme with carbamoyl-phosphate synthase (ammonia) activity; catalyzes the first step of the urea cycle | Central to ammonia detoxification, pyrimidine synthesis, and cancer metabolism |
| OTC | Ornithine transcarbamylase; uses carbamoyl phosphate to form citrulline in the urea cycle | Downstream of CPS1; mutations cause hyperammonaemia |
| ASS1 | Argininosuccinate synthase; next step in urea cycle | Links CPS1 activity to arginine metabolism and tumour growth |
| ASL | Argininosuccinate lyase; urea cycle enzyme | Defects cause argininosuccinic aciduria |
| ARG1 | Arginase 1; final urea cycle enzyme | Modulates ammonia handling and polyamine synthesis |
| NAGS | N-acetylglutamate synthase; produces the essential CPS1 activator N-acetylglutamate | Regulates CPS1 activity allosterically |
| SIRT5 | NAD-dependent desuccinylase that modifies CPS1 | Post-translational regulation of CPS1 activity |
| TP53 | p53 tumour suppressor; regulates urea cycle genes including CPS1 | Links CPS1 to ammonia metabolism and polyamine biosynthesis |
| KRAS | Oncogene; mutant KRAS with LKB1 loss creates dependence on CPS1 | Defines a metabolic vulnerability in lung cancer |
| LKB1 (STK11) | Tumour suppressor; loss with KRAS mutation sensitizes to CPS1 inhibition | Context for CPS1 dependency in lung cancer |
| CAD | Carbamoyl-phosphate synthetase 2, aspartate transcarbamylase, dihydroorotase; cytoplasmic pyrimidine pathway | Contrasts with mitochondrial CPS1 in pyrimidine synthesis |
| GLS | Glutaminase; provides glutamate for ammonia and aspartate metabolism | Supports CPS1-dependent metabolism in cancer |
| GLUD1 | Glutamate dehydrogenase; releases ammonia for CPS1 | Links amino acid catabolism to ureagenesis |
| PC | Pyruvate carboxylase; produces oxaloacetate for aspartate and citrate | Affects intramitochondrial citrate and CPS1 regulation |
| SLC25A15 | Ornithine translocase; transports ornithine into mitochondria | Urea cycle transport; affects CPS1 substrate availability |
| SLC25A13 | Aspartate/glutamate carrier; supports aspartate export | Links CPS1 to aspartate levels and cancer metastasis |
| MDH2 | Malate dehydrogenase; part of TCA cycle | Influences intramitochondrial citrate and CPS1 activity |
How Is carbamoyl-phosphate synthase (ammonia) activity Regulated?
CPS1 activity is regulated at multiple levels. Allosterically, N-acetylglutamate is an essential activator, and its synthesis by NAGS is stimulated by arginine. Intramitochondrial citrate also modulates CPS1, linking the enzyme to the TCA cycle and energy status. Post-translationally, SIRT5 desuccinylates CPS1, which can affect its enzymatic activity. Transcriptional regulation by p53 controls CPS1 expression and ammonia metabolism. In cancer, oncogenic KRAS and loss of LKB1 create a dependency on CPS1 for pyrimidine synthesis. Hormonal and nutritional signals also influence urea cycle flux, as reviewed in the context of non-alcoholic fatty liver disease.
carbamoyl-phosphate synthase (ammonia) activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| CPS1 | KRAS/LKB1-mutant lung cancer; pyrimidine dependency | CPS1 knockout in KRAS/LKB1-mutant lung cancer cell lines; rescue with carbamoyl phosphate or pyrimidines |
| CPS1 | Hepatocellular carcinoma metastasis; aspartate depletion | CPS1 knockout or knockdown in HCC cell lines; aspartate supplementation; metastasis assays |
| CPS1 | Urea cycle disorder / hyperammonaemia | Patient-derived iPSC hepatocytes with CPS1 point mutations; ammonia challenge assays |
| CPS1 | Non-alcoholic fatty liver disease | High-fat diet mouse models with liver-specific Cps1 knockout or overexpression |
| TP53 | p53-mediated regulation of ammonia metabolism and polyamines | p53 knockout or point-mutant cell lines; CPS1 expression and polyamine profiling |
Cancer metabolism and pyrimidine dependency
In KRAS/LKB1-mutant lung cancer, CPS1 maintains pyrimidine pools and DNA synthesis, and its loss impairs tumour growth. In hepatocellular carcinoma, loss of CPS1 reduces aspartate levels and potentiates metastasis, suggesting a complex role in tumour progression. p53 regulation of CPS1 controls ammonia metabolism and polyamine biosynthesis, linking urea cycle activity to tumour suppression.
Urea cycle disorders and hyperammonaemia
CPS1 deficiency is a proximal urea cycle disorder that causes hyperammonaemia. The enzyme's dependence on N-acetylglutamate and its role in ammonia detoxification are central to understanding these disorders. Dysregulation of the urea cycle, including CPS1, is also observed in non-alcoholic fatty liver disease.
Metabolic liver disease
Non-alcoholic fatty liver disease is associated with urea cycle dysregulation, including altered CPS1 expression and activity, which may contribute to hyperammonaemia and disease progression. The link between CPS1 and intramitochondrial citrate further connects hepatic energy metabolism to ureagenesis.
From carbamoyl-phosphate synthase (ammonia) activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of CPS1 affect pyrimidine pools and DNA synthesis? | CPS1 knockout in KRAS/LKB1-mutant lung cancer cells; pyrimidine rescue |
| How does CPS1 loss alter aspartate and metastasis? | CPS1 knockout in hepatocellular carcinoma cells; aspartate measurement and metastasis assays |
| What is the role of SIRT5-mediated desuccinylation on CPS1 activity? | SIRT5 knockout or point-mutant cells; CPS1 succinylation and activity assays |
| How does p53 regulate CPS1 and ammonia metabolism? | p53 knockout or point-mutant cells; CPS1 expression and polyamine profiling |
| Does N-acetylglutamate availability control CPS1 flux? | NAGS knockout or point-mutant hepatocytes; N-acetylglutamate supplementation |
| Can CPS1 overexpression rescue urea cycle defects? | CPS1 knock-in or overexpression in patient-derived cells with CPS1 mutations |
How to Study the carbamoyl-phosphate synthase (ammonia) activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Coupled enzymatic assay | CPS1 catalytic activity | Quantify effects of mutations or allosteric regulators |
| LC-MS metabolomics | Carbamoyl phosphate, pyrimidines, aspartate, urea cycle intermediates | Assess metabolic rewiring after CPS1 loss |
| 13C/15N isotope tracing | Flux through CPS1 and downstream pathways | Determine contribution of CPS1 to pyrimidine and urea synthesis |
| CRISPR knockout + rescue | Causal role of CPS1 in proliferation or metastasis | Cancer cell models |
| Immunoprecipitation + mass spectrometry | Post-translational modifications on CPS1 | Study SIRT5-mediated desuccinylation |
| Western blot | CPS1 protein expression | Validate knockout or overexpression |
| qRT-PCR | CPS1 mRNA levels | Assess transcriptional regulation by p53 |
| Ammonia quantification | Ammonia detoxification capacity | Urea cycle disorder models |
Enzymatic activity assays
CPS1 activity can be measured radiometrically or spectrophotometrically by coupling carbamoyl phosphate production to downstream enzymes. These assays are used to quantify the effect of mutations, allosteric regulators such as N-acetylglutamate, and post-translational modifications.
Metabolomics and flux analysis
Mass spectrometry-based metabolomics can measure carbamoyl phosphate, pyrimidines, aspartate, and urea cycle intermediates. Stable isotope tracing with 15N-ammonia or 13C-bicarbonate allows flux through CPS1 to be quantified in cells and tissues.
Genetic knockout and rescue
CRISPR-Cas9 knockout of CPS1 or related genes, followed by rescue with carbamoyl phosphate, pyrimidines, or aspartate, is used to establish causality in cancer cell proliferation and metastasis models.
Post-translational modification analysis
Immunoprecipitation and mass spectrometry can detect succinylation, acetylation, and other modifications on CPS1. SIRT5 knockout or overexpression models are used to study desuccinylation.
How CRISPR Can Be Used to Study GO:0004087 carbamoyl-phosphate synthase (ammonia) activity
Knockout
CRISPR-Cas9 knockout of CPS1 is used to eliminate carbamoyl-phosphate synthase (ammonia) activity and assess consequences for pyrimidine synthesis, ammonia detoxification, and tumour growth. For example, CPS1 knockout in KRAS/LKB1-mutant lung cancer cells reduces pyrimidine pools and DNA synthesis, which can be rescued by exogenous pyrimidines. In hepatocellular carcinoma, CPS1 knockout reduces aspartate and promotes metastasis.
Point Mutation
Point mutations in CPS1 can be introduced to model inherited urea cycle disorders or to dissect catalytic residues. For instance, mutations affecting N-acetylglutamate binding or ATP hydrolysis can be studied in patient-derived cells to understand hyperammonaemia.
Knock-in
Knock-in of tagged CPS1 (e.g., FLAG or GFP) allows for localization, interaction, and post-translational modification studies. Knock-in of disease-associated mutations can create isogenic models for urea cycle disorders.
Overexpression
Overexpression of CPS1 can rescue loss-of-function phenotypes or enhance ureagenesis and pyrimidine synthesis. It is used to test whether increased CPS1 activity is sufficient to drive metabolic changes, such as increased pyrimidine pools in cancer cells.
How EDITGENE Supports carbamoyl-phosphate synthase (ammonia) activity Research
Researchers studying carbamoyl-phosphate synthase (ammonia) activity-related genes often need to determine whether a candidate gene is causally involved in metabolic rewiring, ammonia detoxification, or tumour growth. EDITGENE provides a comprehensive suite of CRISPR services to generate precisely engineered cell models for such investigations.
Contact EDITGENE today to design your custom CRISPR model for carbamoyl-phosphate synthase (ammonia) activity research.
Frequently Asked Questions About carbamoyl-phosphate synthase (ammonia) activity
What is carbamoyl-phosphate synthase (ammonia) activity?
It is a molecular function defined by GO:0004087 that catalyzes the ATP-dependent formation of carbamoyl phosphate from ammonia and bicarbonate, the first step of the urea cycle.
What genes are involved in carbamoyl-phosphate synthase (ammonia) activity?
The primary gene is CPS1, which encodes the mitochondrial enzyme. Other related genes include NAGS, OTC, ASS1, ASL, ARG1, SIRT5, and TP53.
What is the role of CPS1 in cancer?
CPS1 maintains pyrimidine pools and DNA synthesis in KRAS/LKB1-mutant lung cancer, and its loss reduces aspartate and promotes metastasis in hepatocellular carcinoma.
How is CPS1 activity regulated?
CPS1 is allosterically activated by N-acetylglutamate, modulated by intramitochondrial citrate, and post-translationally modified by SIRT5-mediated desuccinylation.
What diseases are associated with CPS1 dysfunction?
CPS1 deficiency causes hyperammonaemia and urea cycle disorders. Dysregulation is also seen in non-alcoholic fatty liver disease and cancer.
What is the reaction catalyzed by carbamoyl-phosphate synthase (ammonia)?
2 ATP + hydrogencarbonate + NH4+ = 2 ADP + carbamoyl phosphate + 2 H+ + phosphate.
How can I study carbamoyl-phosphate synthase (ammonia) activity in the lab?
Common methods include coupled enzymatic assays, metabolomics, isotope tracing, and CRISPR knockout models.
What is the difference between CPS1 and CPS2?
CPS1 uses ammonia and is mitochondrial, while CPS2 (CAD) uses glutamine and is cytoplasmic, participating in pyrimidine synthesis.
Why is CPS1 important for liver function?
CPS1 is the rate-limiting enzyme of the urea cycle, which detoxifies ammonia in the liver.
Can CRISPR be used to model CPS1 deficiency?
Yes, CRISPR knockout or point mutation of CPS1 in cell models can recapitulate urea cycle defects and hyperammonaemia.
Conclusion
Carbamoyl-phosphate synthase (ammonia) activity, GO:0004087, is a fundamental mitochondrial function that links ammonia detoxification, pyrimidine synthesis, and energy metabolism. Its dysregulation contributes to cancer progression, liver disease, and inherited hyperammonaemia. Studying this activity with CRISPR models and metabolic assays provides insights into nitrogen homeostasis and identifies potential therapeutic targets.
References
- 1. Kim J et al.. 2017. CPS1 maintains pyrimidine pools and DNA synthesis in KRAS/LKB1-mutant lung cancer cells.. Nature 546(7656):168-172 PMID: 28538732
- 2. Du J et al.. 2011. Sirt5 is a NAD-dependent protein lysine demalonylase and desuccinylase.. Science 334(6057):806-9 PMID: 22076378
- 3. Li L et al.. 2019. p53 regulation of ammonia metabolism through urea cycle controls polyamine biosynthesis.. Nature 567(7747):253-256 PMID: 30842655
- 4. Chen S et al.. 2024. Loss of Carbamoyl Phosphate Synthetase 1 Potentiates Hepatocellular Carcinoma Metastasis by Reducing Aspartate Level.. Adv Sci (Weinh) 11(45):e2402703 PMID: 39387452
- 5. Meijer AJ et al.. 1977. Relationship between intramitochondrial citrate and the activity of carbamoyl-phosphate synthase (ammonia).. Biochim Biophys Acta 500(1):13-26 PMID: 21702
- 6. Meijer AJ et al.. 1985. Control of ureogenesis.. Eur J Biochem 148(1):189-96 PMID: 3979393
- 7. De Chiara F et al.. 2018. Urea cycle dysregulation in non-alcoholic fatty liver disease.. J Hepatol 69(4):905-915 PMID: 29981428
