GO:0004055 argininosuccinate synthase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0004055 (argininosuccinate synthase activity) is a molecular function that catalyzes the ATP-dependent ligation of L-citrulline and L-aspartate to form (N(omega)-L-arginino)succinate (argininosuccinate), AMP, and diphosphate.
• The enzyme is encoded primarily by ASS1, and loss-of-function mutations in ASS1 cause citrullinemia type 1, an inherited urea cycle disorder with variable phenotypic severity.
• ASS1-mediated citrulline depletion is required for proinflammatory macrophage activation, linking this metabolic activity to innate immune responses.
• In cancer, ASS1 expression is frequently altered; oncogenic KRAS induces arginine auxotrophy and creates a therapeutic vulnerability to SLC7A1 inhibition in non-small cell lung cancer.
• Blocking ASS1 alleviates colitis in mice, indicating that argininosuccinate synthase activity contributes to intestinal inflammation.
• Arginine biosynthesis, which depends on argininosuccinate synthase activity, can be enhanced by dietary polysaccharides to alleviate colitis, highlighting its therapeutic potential.
Description
Argininosuccinate synthase activity (GO:0004055) is a fundamental molecular function in nitrogen metabolism, catalyzing the ATP-dependent condensation of L-citrulline and L-aspartate to form argininosuccinate, AMP, and diphosphate. This reaction is a critical step in the urea cycle and in arginine biosynthesis, and its dysregulation has profound consequences for human health. The enzyme responsible, argininosuccinate synthetase 1 (ASS1), is one of the most studied urea cycle enzymes due to its role in citrullinemia type 1 and its emerging importance in immunology and oncology. Researchers across disciplines study argininosuccinate synthase activity because it sits at the intersection of amino acid metabolism, immune cell function, and cancer cell proliferation. For example, ASS1-mediated citrulline depletion is required for proinflammatory macrophage activation, directly linking this enzymatic activity to immune responses. In cancer, oncogenic KRAS induces arginine auxotrophy, and ASS1 status influences sensitivity to arginine deprivation strategies. Furthermore, blocking ASS1 alleviates colitis in mice, suggesting that modulating this activity could be therapeutically beneficial in inflammatory bowel disease. Given its broad relevance, argininosuccinate synthase activity is a prime target for functional genomics. Understanding its catalytic mechanism, regulation, and role in disease requires robust experimental models, including CRISPR knockout, point mutation, and knock-in cell lines. This article provides a comprehensive overview of GO:0004055, integrating authoritative QuickGO data with verified PubMed literature to support researchers in designing and interpreting experiments.
argininosuccinate synthase activity At A Glance
| GO ID | GO:0004055 |
|---|---|
| GO term | argininosuccinate synthase activity |
| Ontology | molecular_function |
| Synonym | arginine succinate synthetase activity; argininosuccinate synthetase activity; argininosuccinic acid synthetase activity; arginosuccinate synthetase activity; citrulline--aspartate ligase activity; L-citrulline:L-aspartate ligase (AMP-forming) |
| Definition | Catalysis of the reaction: ATP + L-citrulline + L-aspartate = AMP + diphosphate + (N(omega)-L-arginino)succinate. |
| Major function | Catalyzes the third step of the urea cycle and a key step in arginine biosynthesis. |
| EC number | 6.3.4.5 |
| Primary gene | ASS1 (argininosuccinate synthetase 1) |
| Related pathway | Urea cycle; arginine biosynthesis; amino acid metabolism. |
What Is GO:0004055?
Argininosuccinate synthase activity (GO:0004055) is defined as the catalysis of the reaction: ATP + L-citrulline + L-aspartate = AMP + diphosphate + (N(omega)-L-arginino)succinate. In simpler terms, it is the enzymatic activity that joins citrulline and aspartate together using ATP energy to produce argininosuccinate, a precursor for arginine synthesis. This activity is synonymous with arginine succinate synthetase activity, argininosuccinate synthetase activity, argininosuccinic acid synthetase activity, arginosuccinate synthetase activity, citrulline--aspartate ligase activity, and L-citrulline:L-aspartate ligase (AMP-forming).
Why Is argininosuccinate synthase activity Important in Cell Biology?
Argininosuccinate synthase activity is essential for nitrogen disposal via the urea cycle and for the endogenous synthesis of arginine, a conditionally essential amino acid with wide-ranging roles in cell signaling, immunity, and proliferation. Its dysfunction causes citrullinemia type 1, a severe metabolic disorder, and its altered expression is implicated in cancer, inflammation, and immune regulation. Consequently, understanding this activity is critical for developing diagnostics, prognostics, and targeted therapies.
• Defects in ASS1, the enzyme catalyzing GO:0004055, cause citrullinemia type 1, a urea cycle disorder with potentially fatal hyperammonemia.
• ASS1-mediated citrulline depletion is required for proinflammatory macrophage activation and immune responses.
• Oncogenic KRAS induces arginine auxotrophy in non-small cell lung cancer, creating a vulnerability to SLC7A1 inhibition.
• Blocking ASS1 alleviates colitis in mice, suggesting a role in intestinal inflammation.
• Arginine biosynthesis, which depends on argininosuccinate synthase activity, can be enhanced by Crataegus pinnatifida polysaccharide to alleviate DSS-induced colitis.
• ASS1 expression is frequently downregulated in various cancers, making it a potential tumor suppressor and biomarker.
• The reaction is a key step in the urea cycle, linking amino acid catabolism to nitrogen excretion.
• Argininosuccinate synthase activity is a target for therapeutic intervention in metabolic disorders and cancer.
• Understanding its regulation provides insights into metabolic reprogramming in immune cells.
• CRISPR-based models of ASS1 mutations enable precise study of genotype-phenotype relationships in citrullinemia.
Molecular Mechanism of argininosuccinate synthase activity
Substrate Binding and Catalysis
In simple terms: The enzyme grabs citrulline and aspartate, uses ATP to power their joining, and releases argininosuccinate.
Argininosuccinate synthase (ASS1) catalyzes the ATP-dependent ligation of L-citrulline and L-aspartate to form (N(omega)-L-arginino)succinate (argininosuccinate), AMP, and diphosphate. The reaction proceeds through an adenylated intermediate, where the enzyme first activates citrulline by transferring AMP from ATP, followed by nucleophilic attack by aspartate. This mechanism is conserved across species and is essential for the urea cycle and arginine biosynthesis.
Cofactors and Energetics
In simple terms: ATP provides the energy, and the reaction releases AMP and diphosphate as byproducts.
The reaction consumes one molecule of ATP and produces AMP and diphosphate, making it energetically costly. This irreversibility under physiological conditions drives the urea cycle forward. No additional cofactors are required for catalysis, although magnesium ions may stabilize the ATP-binding site.
Structural Features of ASS1
In simple terms: The enzyme has a specific shape that fits its substrates and allows the reaction to happen.
ASS1 is a homotetramer in humans, with each subunit containing a catalytic domain that binds citrulline and aspartate. Mutations in ASS1 that impair tetramerization or substrate binding lead to reduced enzymatic activity and are associated with citrullinemia type 1. Structural studies have identified common mutations, such as p.Gly390Arg, that affect the active site and are linked to severe phenotypes.
Regulation of Enzyme Activity
In simple terms: The enzyme's activity can be turned up or down by cellular signals and substrate availability.
ASS1 expression and activity are regulated at multiple levels. In proinflammatory macrophages, citrulline depletion by ASS1 is required for activation, suggesting that substrate availability and enzyme expression are tightly controlled. In cancer, oncogenic KRAS can induce arginine auxotrophy by modulating ASS1 expression, making cells dependent on exogenous arginine. Additionally, ASS1 activity can be influenced by inflammatory signals and metabolic stress.
Key Genes Involved in GO:0004055 argininosuccinate synthase activity
The following genes and proteins are directly or indirectly involved in argininosuccinate synthase activity, its regulation, and its physiological consequences.
| Gene | Major Role | Research Relevance |
|---|---|---|
| ASS1 | Encodes argininosuccinate synthetase 1, the enzyme catalyzing GO:0004055 | Mutations cause citrullinemia type 1; expression altered in cancer and inflammation |
| ASL | Encodes argininosuccinate lyase, the next enzyme in the urea cycle | Defects cause argininosuccinic aciduria; interacts with ASS1 pathway |
| OTC | Encodes ornithine transcarbamylase, upstream of ASS1 in the urea cycle | Defects cause OTC deficiency; provides substrate for ASS1 |
| CPS1 | Encodes carbamoyl phosphate synthetase 1, upstream of ASS1 | Defects cause CPS1 deficiency; affects citrulline availability |
| ARG1 | Encodes arginase 1, competes with ASS1 for arginine | Regulates arginine availability; linked to immune suppression |
| NOS2 | Encodes inducible nitric oxide synthase, consumes arginine | Competes with ASS1 for arginine; affects macrophage function |
| SLC7A1 | Encodes cationic amino acid transporter 1, imports arginine | Target in KRAS-driven cancers with arginine auxotrophy |
| SLC7A2 | Encodes cationic amino acid transporter 2, imports arginine | Modulates arginine availability in immune cells |
| KRAS | Oncogene that induces arginine auxotrophy | Mutations in KRAS create vulnerability to arginine deprivation |
| AQP5 | Aquaporin 5, involved in arginine deprivation in gastric cancer stem cells | Targeting AQP5 restores NK cell anti-tumor immunity |
| HIF1A | Hypoxia-inducible factor 1 alpha, regulates metabolic genes | May influence ASS1 expression under hypoxia |
| MYC | Oncogene that regulates metabolism | Can affect arginine metabolism and ASS1 expression |
| ATF4 | Transcription factor in integrated stress response | Regulates amino acid metabolism genes including ASS1 |
| C/EBPβ | Transcription factor involved in macrophage activation | May regulate ASS1 expression during inflammation |
| NF-κB | Inflammatory transcription factor | Links ASS1 activity to proinflammatory signaling |
| IL-1β | Proinflammatory cytokine | Induced upon macrophage activation dependent on ASS1 |
| TNF-α | Proinflammatory cytokine | Part of immune response linked to ASS1 activity |
| Fumarate hydratase (FH) | Metabolic enzyme mutated in hereditary leiomyomatosis and renal cell cancer | Loss leads to mtRNA-mediated interferon production, potentially interacting with arginine metabolism |
How Is argininosuccinate synthase activity Regulated?
Argininosuccinate synthase activity is regulated at transcriptional, post-transcriptional, and metabolic levels. In proinflammatory macrophages, ASS1 expression is induced to deplete citrulline, a process required for activation and cytokine production. This induction is likely mediated by transcription factors such as ATF4 and C/EBPβ, which respond to metabolic stress and inflammatory signals. In cancer, oncogenic KRAS can suppress ASS1 expression, leading to arginine auxotrophy and dependence on exogenous arginine. Additionally, substrate availability (citrulline and aspartate) and product inhibition by argininosuccinate may modulate enzyme activity. The integrated stress response (ISR) can also influence ASS1 expression through ATF4, linking amino acid deprivation to urea cycle regulation.
argininosuccinate synthase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| ASS1 | Citrullinemia type 1 | Knockout or point-mutation (e.g., p.Gly390Arg) in hepatocytes or iPSCs |
| ASS1 | Colitis | Knockout in intestinal epithelial cells or macrophages |
| ASS1 | Cancer (arginine auxotrophy) | Knockout in KRAS-mutant lung cancer cell lines |
| SLC7A1 | Non-small cell lung cancer | Knockout or overexpression in cancer cells |
| AQP5 | Gastric cancer stem cells | Knockout in gastric cancer organoids |
Citrullinemia Type 1
Citrullinemia type 1 is an autosomal recessive urea cycle disorder caused by mutations in ASS1, leading to reduced argininosuccinate synthase activity. Patients present with hyperammonemia, elevated plasma citrulline, and neurological symptoms. Early prediction of phenotypic severity is critical for management, and specific mutations such as p.Gly390Arg are associated with severe neonatal-onset disease. CRISPR-based models of ASS1 mutations can help dissect genotype-phenotype correlations and test therapeutic strategies.
Cancer and Arginine Auxotrophy
Many cancers exhibit altered ASS1 expression, leading to arginine auxotrophy. In non-small cell lung cancer, oncogenic KRAS induces arginine auxotrophy and confers sensitivity to SLC7A1 inhibition. Similarly, targeting AQP5-mediated arginine deprivation in gastric cancer stem cells restores NK cell anti-tumor immunity. These findings highlight argininosuccinate synthase activity as a metabolic vulnerability in cancer and a potential target for therapy.
Inflammatory Bowel Disease
Blocking ASS1 alleviates colitis in mice, indicating that argininosuccinate synthase activity contributes to intestinal inflammation. Additionally, enhancing arginine biosynthesis via Crataegus pinnatifida polysaccharide alleviates DSS-induced colitis by regulating gut microbiota. These studies suggest that modulating this activity could be therapeutic in inflammatory bowel disease.
Immune Regulation
ASS1-mediated citrulline depletion is required for proinflammatory macrophage activation and immune responses. This links argininosuccinate synthase activity to innate immunity and suggests that its inhibition could dampen excessive inflammation. Furthermore, macrophage fumarate hydratase restrains mtRNA-mediated interferon production, revealing a broader metabolic control of immune responses.
From argininosuccinate synthase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| What is the effect of ASS1 loss on urea cycle flux? | ASS1 knockout hepatocyte cell line (HepG2) |
| How do specific ASS1 mutations affect enzyme activity? | Point-mutation knock-in (e.g., p.Gly390Arg) in iPSCs |
| Does ASS1 overexpression alter macrophage activation? | ASS1 overexpression in THP-1 macrophages |
| Can ASS1 knockout sensitize cancer cells to arginine deprivation? | ASS1 knockout in KRAS-mutant NSCLC cells |
| What is the role of ASS1 in colitis? | Intestinal epithelial cell-specific ASS1 knockout mice |
| How does ASS1 interact with other metabolic enzymes? | Tagged knock-in (e.g., FLAG-ASS1) for immunoprecipitation |
How to Study the argininosuccinate synthase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Enzymatic activity assay | Argininosuccinate synthase catalytic activity | Validation of ASS1 mutations |
| Metabolomics | Levels of citrulline, arginine, and related metabolites | Assessing metabolic impact of ASS1 modulation |
| Proteomics | Protein expression and interactions | Identifying ASS1 binding partners |
| CRISPR knockout screening | Gene essentiality and synthetic lethality | Finding vulnerabilities in ASS1-deficient cancers |
| RNA-seq | Transcriptional changes upon ASS1 manipulation | Understanding regulatory networks |
| Western blot | ASS1 protein expression | Validating knockout or overexpression |
| Immunofluorescence | Subcellular localization of ASS1 | Studying enzyme distribution |
| CRISPR knock-in | Introduction of specific mutations | Modeling citrullinemia mutations |
Enzymatic Activity Assays
Direct measurement of argininosuccinate synthase activity can be performed using coupled spectrophotometric assays that monitor the consumption of ATP or the production of AMP. These assays are essential for validating the functional impact of ASS1 mutations identified in patients.
Metabolomics and Proteomics
Metabolomics and proteomics have been used to reveal that blocking ASS1 alleviates colitis in mice, highlighting the importance of global metabolic profiling. Such approaches can identify changes in citrulline, arginine, and related metabolites upon modulation of argininosuccinate synthase activity.
CRISPR Screening and Functional Genomics
CRISPR knockout screens can identify genes that modulate sensitivity to arginine deprivation, as demonstrated in KRAS-mutant lung cancer. These screens are powerful for uncovering synthetic lethal interactions with ASS1 loss.
Imaging and Reporter Assays
Fluorescent reporters or tagged ASS1 can be used to visualize enzyme localization and dynamics in live cells. This is particularly useful for studying ASS1 in immune cells and cancer cells.
How CRISPR Can Be Used to Study GO:0004055 argininosuccinate synthase activity
Knockout
CRISPR knockout of ASS1 can create cell models to study the consequences of loss of argininosuccinate synthase activity. These models are valuable for investigating urea cycle dysfunction, arginine auxotrophy, and immune cell activation.
Point Mutation
Point mutations in ASS1, such as p.Gly390Arg, can be introduced using CRISPR base editing or homology-directed repair to model citrullinemia type 1 and assess genotype-phenotype relationships.
Knock-in
Knock-in of tagged ASS1 (e.g., FLAG or GFP) allows for tracking enzyme localization, interaction partners, and dynamics in live cells, facilitating studies of its regulation and function.
Overexpression
Overexpression of ASS1 via CRISPR activation or lentiviral delivery can be used to study the effects of increased argininosuccinate synthase activity on cell metabolism, immune responses, and cancer progression.
How EDITGENE Supports argininosuccinate synthase activity Research
Researchers studying argininosuccinate synthase activity-related genes often need to determine whether a candidate gene is causally involved in metabolic, immune, or cancer phenotypes. EDITGENE provides a comprehensive suite of CRISPR-based services to generate precisely engineered cell models, enabling rigorous functional validation of genes like ASS1 and its regulators.
Contact EDITGENE today to design your custom CRISPR model for argininosuccinate synthase activity research.
Related Products
| Product name | Cat.No. | Species | Gene ID | |
|---|---|---|---|---|
| ASS1 Knockout HEK293 Cell Line | EDJ-KQ4105 | Human | 445 | Details Get a Quote |
| ASS1 Knockout HCT 116 Cell Line | EDJ-KQ25163 | Human | 445 | Details Get a Quote |
| ASS1 Knockout A-549 Cell Line | EDJ-KQ26497 | Human | 445 | Details Get a Quote |
| ASS1 Knockout HeLa Cell Line | EDJ-KQ26499 | Human | 445 | Details Get a Quote |
Displaying Records 1 To 4 Of 4 Records
Frequently Asked Questions About argininosuccinate synthase activity
What is argininosuccinate synthase activity?
Argininosuccinate synthase activity (GO:0004055) is the enzymatic function that catalyzes the ATP-dependent joining of citrulline and aspartate to form argininosuccinate, AMP, and diphosphate.
What genes are involved in argininosuccinate synthase activity?
The primary gene is ASS1, which encodes argininosuccinate synthetase 1. Other related genes include ASL, OTC, CPS1, and ARG1 in the urea cycle.
What diseases are associated with argininosuccinate synthase activity?
Mutations in ASS1 cause citrullinemia type 1. Altered activity is also implicated in cancer, colitis, and immune regulation.
How is argininosuccinate synthase activity regulated?
It is regulated by transcriptional factors like ATF4 and C/EBPβ, substrate availability, and oncogenic signals such as KRAS.
What is the role of ASS1 in cancer?
ASS1 loss can lead to arginine auxotrophy, making cancer cells dependent on exogenous arginine and sensitive to arginine deprivation therapies.
How can I study argininosuccinate synthase activity in the lab?
Common methods include enzymatic activity assays, metabolomics, CRISPR knockout/knock-in models, and proteomics.
What is citrullinemia type 1?
Citrullinemia type 1 is an inherited urea cycle disorder caused by ASS1 mutations, leading to hyperammonemia and neurological symptoms.
Does argininosuccinate synthase activity play a role in immunity?
Yes, ASS1-mediated citrulline depletion is required for proinflammatory macrophage activation and immune responses.
Can CRISPR be used to model ASS1 mutations?
Yes, CRISPR knockout, point mutation knock-in, and overexpression models are widely used to study ASS1 function and disease.
What are the synonyms for argininosuccinate synthase activity?
Synonyms include arginine succinate synthetase activity, argininosuccinate synthetase activity, argininosuccinic acid synthetase activity, arginosuccinate synthetase activity, citrulline--aspartate ligase activity, and L-citrulline:L-aspartate ligase (AMP-forming).
Conclusion
Argininosuccinate synthase activity (GO:0004055) is a central metabolic function with far-reaching implications for urea cycle disorders, cancer, and immune regulation. The enzyme ASS1, which catalyzes this reaction, is a critical node in arginine biosynthesis and nitrogen disposal, and its dysfunction underlies citrullinemia type 1. Emerging evidence links ASS1 activity to proinflammatory macrophage activation, colitis, and cancer arginine auxotrophy, making it a compelling target for therapeutic intervention. Researchers can leverage CRISPR-based models, including knockout, point mutation, knock-in, and overexpression cell lines, to dissect the molecular mechanisms and disease relevance of argininosuccinate synthase activity. EDITGENE provides end-to-end services to support these efforts, from custom cell line generation to CRISPR library screening and bioinformatics analysis.
References
- 1. Hooftman A et al.. 2023. Macrophage fumarate hydratase restrains mtRNA-mediated interferon production.. Nature 615(7952):490-498 PMID: 36890227
- 2. Liu S et al.. 2025. Metabolomics and proteomics reveal blocking argininosuccinate synthetase 1 alleviates colitis in mice.. Nat Commun 16(1):6983 PMID: 40739098
- 3. Zielonka M et al.. 2019. Early prediction of phenotypic severity in Citrullinemia Type 1.. Ann Clin Transl Neurol 6(9):1858-1871 PMID: 31469252
- 4. Wei FH et al.. 2025. Crataegus pinnatifida polysaccharide alleviates DSS-induced colitis in mice by regulating the intestinal microbiota and enhancing arginine biosynthesis.. Phytomedicine 142:156794 PMID: 40315641
- 5. Diez-Fernandez C et al.. 2017. Mutations in the Human Argininosuccinate Synthetase (ASS1) Gene, Impact on Patients, Common Changes, and Structural Considerations.. Hum Mutat 38(5):471-484 PMID: 28111830
- 6. Mao Y et al.. 2022. Citrulline depletion by ASS1 is required for proinflammatory macrophage activation and immune responses.. Mol Cell 82(3):527-541.e7 PMID: 35016033
- 7. Zhao R et al.. 2025. Targeting AQP5-mediated arginine deprivation in gastric cancer stem cells restores NK cell anti-tumor immunity.. Cell Rep Med 6(9):102333 PMID: 40961922
- 8. Gai X et al.. 2024. Oncogenic KRAS Induces Arginine Auxotrophy and Confers a Therapeutic Vulnerability to SLC7A1 Inhibition in Non-Small Cell Lung Cancer.. Cancer Res 84(12):1963-1977 PMID: 38502865
