GO:0004070 aspartate carbamoyltransferase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0004070 defines aspartate carbamoyltransferase (ATCase) activity, which catalyzes the committed step of de novo pyrimidine biosynthesis: L-aspartate + carbamoyl phosphate = N-carbamoyl-L-aspartate + phosphate.
• ATCase is a classic model for allosteric regulation and cooperativity, with activity modulated by metal cations and nucleotide effectors.
• The enzyme is widely expressed across tissues, with activity detected in liver, ovine tissues, hematopoietic organs, and embryos.
• ATCase activity is frequently measured by HPLC-based assays, which enable precise quantification in biological samples.
• In cancer, CAD (the multifunctional enzyme containing ATCase) is activated by PFKFB3 to enhance de novo pyrimidine synthesis and support cell growth.
• CRISPR-based models (knockout, point mutation, knock-in, overexpression) are essential to dissect the causal roles of ATCase-containing proteins in disease and development.
Description
Aspartate carbamoyltransferase (ATCase) activity, encoded by GO:0004070, is a molecular function that catalyzes the committed step in de novo pyrimidine biosynthesis: the condensation of L-aspartate with carbamoyl phosphate to form N-carbamoyl-L-aspartate, phosphate, and a proton. This reaction is essential for the production of uridine monophosphate (UMP), the precursor of all pyrimidine nucleotides required for RNA and DNA synthesis. Because of its central role in nucleotide metabolism, ATCase activity has been studied for decades as a paradigm of allosteric regulation and enzyme cooperativity. Researchers value GO:0004070 not only for its biochemical significance but also for its implications in cell growth, development, and disease. The enzyme is present in organisms from bacteria to mammals, and its activity has been documented in diverse tissues, including rat liver, ovine tissues, loach embryos, and hematopoietic organs. In cancer, the CAD protein (which harbors ATCase activity) is activated by PFKFB3 to boost pyrimidine synthesis, highlighting the pathway as a potential therapeutic target. This article provides a comprehensive overview of GO:0004070, covering its definition, biological importance, molecular mechanism, key genes, regulatory features, disease associations, and the experimental methods used to study it. Emphasis is placed on CRISPR-based approaches that enable precise genetic manipulation of ATCase-related genes for functional studies.
aspartate carbamoyltransferase activity At A Glance
| GO ID | GO:0004070 |
|---|---|
| GO term | aspartate carbamoyltransferase activity |
| Ontology | molecular_function |
| Synonym | ATCase activity; aspartate transcarbamoylase activity; L-aspartate transcarbamylase activity |
| Major function | Catalyzes the committed step of de novo pyrimidine biosynthesis |
| Reaction | L-aspartate + carbamoyl phosphate = N-carbamoyl-L-aspartate + H+ + phosphate |
| Cofactors | Metal cations can influence activity and regulation |
| Regulation | Allosteric regulation by nucleotides and metal ions |
| Pathway | De novo pyrimidine biosynthesis |
What Is GO:0004070?
GO:0004070, aspartate carbamoyltransferase activity, is defined as the catalysis of the reaction: L-aspartate + carbamoyl phosphate = N-carbamoyl-L-aspartate + H+ + phosphate. In simpler terms, it is the enzyme activity that joins aspartate and carbamoyl phosphate to produce N-carbamoyl-L-aspartate, a key intermediate in pyrimidine biosynthesis. This activity is synonymous with aspartate transcarbamoylase (ATCase) activity and represents the first committed step of the de novo pyrimidine pathway.
Why Is aspartate carbamoyltransferase activity Important in Cell Biology?
GO:0004070 is critically important because it governs the first committed step of de novo pyrimidine biosynthesis, a pathway that supplies the nucleotides needed for DNA replication, RNA transcription, and cell proliferation. Dysregulation of this activity can lead to imbalances in nucleotide pools, which are associated with cancer, developmental defects, and metabolic disorders. Moreover, ATCase serves as a textbook example of allosteric regulation, providing fundamental insights into protein cooperativity and metabolic control.
• Provides precursors for DNA and RNA synthesis, essential for cell division and growth.
• Serves as a model system for studying allosteric regulation and cooperativity.
• Activity is developmentally regulated, as shown in rat liver at different stages.
• Detected in multiple tissues, including ovine tissues and hematopoietic organs.
• Influenced by metal cations, linking enzyme activity to cellular metal homeostasis.
• Targeted by cancer research because CAD activation enhances pyrimidine synthesis.
• Measurable by HPLC, enabling clinical and preclinical studies.
• Studied in embryos, indicating roles in early development.
Molecular Mechanism of aspartate carbamoyltransferase activity
Substrate Binding and Catalysis
In simple terms: The enzyme grabs two molecules and joins them together.
ATCase binds L-aspartate and carbamoyl phosphate in its active site. The reaction proceeds via a nucleophilic attack of the aspartate amino group on the carbonyl carbon of carbamoyl phosphate, forming N-carbamoyl-L-aspartate and releasing phosphate and a proton. This catalytic step is the committed step of pyrimidine biosynthesis.
Allosteric Regulation
In simple terms: Other molecules can switch the enzyme's activity up or down.
ATCase from Escherichia coli is a classic allosteric enzyme regulated by nucleotide effectors such as ATP (activator) and CTP (inhibitor). This feedback regulation ensures balanced pyrimidine pools. Metal cations also influence activity and regulation, as shown in early studies.
Metal Cation Influence
In simple terms: Metal ions can change how well the enzyme works.
Metal cations such as zinc or cadmium can modulate ATCase activity and its allosteric properties. This suggests that cellular metal homeostasis may impact pyrimidine synthesis.
Structural Organization
In simple terms: The enzyme is built from multiple parts that work together.
In E. coli, ATCase is a dodecamer composed of six catalytic and six regulatory subunits, arranged as two catalytic trimers and three regulatory dimers. This quaternary structure is essential for cooperativity and allosteric regulation.
Tissue-Specific Expression and Activity
In simple terms: Different tissues have different amounts of this enzyme.
ATCase activity varies across tissues and developmental stages. For example, activity has been measured in rat liver during development, in ovine tissues, and in hematopoietic organs after DNA injection. These variations reflect tissue-specific demands for pyrimidine nucleotides.
Key Genes Involved in GO:0004070 aspartate carbamoyltransferase activity
The following genes and proteins are directly or indirectly associated with aspartate carbamoyltransferase activity (GO:0004070) and its regulation.
| Gene | Major Role | Research Relevance |
|---|---|---|
| CAD | Multifunctional enzyme with ATCase activity in mammals | Target of PFKFB3 activation in cancer |
| pyrB | E. coli ATCase catalytic subunit | Model for allosteric regulation |
| pyrI | E. coli ATCase regulatory subunit | Allosteric regulation by CTP/ATP |
| PFKFB3 | Activates CAD to enhance pyrimidine synthesis | Cancer metabolism target |
| UMPS | Downstream enzyme in pyrimidine synthesis | Links ATCase to UMP production |
| DHODH | Mitochondrial enzyme in pyrimidine synthesis | Target for inhibitors |
| CTPS1 | CTP synthase, downstream of ATCase | Feedback regulation |
| ATIC | Bifunctional enzyme in purine synthesis | Purine-pyrimidine balance |
| GART | Purine synthesis enzyme | Nucleotide pool coordination |
| MTOR | Regulates pyrimidine synthesis via CAD phosphorylation | Growth signaling |
| AMPK | Energy sensor that may affect pyrimidine synthesis | Metabolic regulation |
| MYC | Oncogene that drives nucleotide synthesis | Cancer proliferation |
| TP53 | Tumor suppressor affecting metabolism | Stress response |
| KRAS | Oncogene linked to metabolic reprogramming | Cancer therapy |
| EGFR | Receptor tyrosine kinase affecting growth | Signaling to pyrimidine synthesis |
| PIK3CA | PI3K subunit, activates AKT/mTOR | Growth signaling |
| PTEN | Tumor suppressor, negative regulator of PI3K | Metabolic control |
| RB1 | Cell cycle regulator | Proliferation control |
How Is aspartate carbamoyltransferase activity Regulated?
ATCase activity is regulated at multiple levels. In E. coli, it is allosterically inhibited by CTP and activated by ATP, providing feedback control of pyrimidine biosynthesis. Metal cations can also modulate activity and regulation. In mammals, the CAD protein is phosphorylated and activated by mTOR signaling, and PFKFB3 has been shown to activate CAD to enhance de novo pyrimidine synthesis for cell growth. Developmental and tissue-specific regulation has been observed, with activity changing during rat liver development and varying among ovine tissues.
aspartate carbamoyltransferase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| CAD | Cancer (pyrimidine synthesis) | Knockout or point mutation in cancer cell lines |
| PFKFB3 | Cancer metabolism | Overexpression or knockout in tumor models |
| pyrB | Bacterial infections (target) | Knockout in E. coli for antibiotic studies |
| pyrI | Bacterial infections (target) | Point mutations to study allostery |
| UMPS | Orotic aciduria | Knock-in of patient mutations |
Cancer
Dysregulated pyrimidine synthesis supports rapid cancer cell proliferation. PFKFB3 activates CAD, the mammalian enzyme with ATCase activity, to enhance de novo pyrimidine synthesis, making this pathway a potential target for cancer therapy.
Developmental Disorders
ATCase activity is developmentally regulated, as shown in rat liver at different stages. Disruption of pyrimidine synthesis during development could lead to growth defects, though direct links to human developmental disorders require further study.
Hematological and Metabolic Stress
ATCase activity in hematopoietic organs changes after DNA injection, suggesting a role in stress responses and tissue regeneration. This may have implications for blood disorders and regenerative medicine.
From aspartate carbamoyltransferase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of ATCase activity impair cell proliferation? | CRISPR knockout of CAD or pyrB |
| How do point mutations affect allosteric regulation? | CRISPR point mutation in pyrB/pyrI |
| Can a disease-associated mutation be corrected? | Knock-in of wild-type allele |
| Where is ATCase expressed in tissues? | Tagged knock-in with fluorescent reporter |
| Does overexpression drive pyrimidine synthesis? | CRISPR overexpression of CAD |
| What genes interact with ATCase? | CRISPR library screening |
How to Study the aspartate carbamoyltransferase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| HPLC | ATCase activity by substrate/product quantification | Tissue and cell extracts |
| Spectrophotometry | Enzyme activity via colorimetric assay | Developmental studies |
| CRISPR knockout | Loss-of-function effects on pyrimidine synthesis | Cancer cell lines |
| CRISPR activation | Gain-of-function of CAD or related genes | Metabolic studies |
| Metabolomics | Levels of pyrimidine intermediates | Flux analysis |
| Western blot | Protein expression of CAD | Regulation studies |
| qPCR | mRNA levels of CAD, pyrB | Expression profiling |
HPLC-Based Activity Assay
High-performance liquid chromatography (HPLC) can measure ATCase activity by quantifying the formation of N-carbamoyl-L-aspartate or consumption of substrates. This method is sensitive and suitable for tissue samples.
Enzymatic Assays in Tissues
Classical spectrophotometric assays have been used to measure ATCase activity in rat liver, ovine tissues, and hematopoietic organs. These assays typically couple the reaction to a colorimetric readout.
CRISPR Screening
Genome-wide CRISPR knockout or activation screens can identify genes that regulate ATCase activity or pyrimidine synthesis. Such screens are powerful for discovering novel regulators.
Metabolomics and Flux Analysis
Mass spectrometry-based metabolomics can quantify pyrimidine intermediates and flux through the pathway, providing a functional readout of ATCase activity in cells.
How CRISPR Can Be Used to Study GO:0004070 aspartate carbamoyltransferase activity
Knockout
CRISPR knockout of CAD or bacterial pyrB eliminates ATCase activity, allowing researchers to test its requirement for cell proliferation and pyrimidine synthesis. Knockout models are essential for validating dependency.
Point Mutation
Introducing point mutations in the active site or allosteric sites of ATCase can dissect catalytic and regulatory mechanisms. For example, mutations in pyrB or pyrI can alter allosteric regulation.
Knock-in
Knock-in of disease-associated or tagged alleles enables precise tracking of ATCase expression and function in vivo. This is useful for studying developmental regulation.
Overexpression
CRISPR activation or cDNA overexpression of CAD can boost pyrimidine synthesis, mimicking cancer-associated metabolic reprogramming. Overexpression models help identify downstream effects.
How EDITGENE Supports aspartate carbamoyltransferase activity Research
Researchers studying aspartate carbamoyltransferase activity-related genes often need to determine whether a candidate gene is causally involved in pyrimidine synthesis, cell growth, or disease. EDITGENE provides a comprehensive suite of CRISPR services to generate precisely engineered cell models for such functional studies.
Contact EDITGENE today to design your custom CRISPR model for aspartate carbamoyltransferase activity research.
Frequently Asked Questions About aspartate carbamoyltransferase activity
What is aspartate carbamoyltransferase activity?
It is the enzyme activity (GO:0004070) that catalyzes the reaction L-aspartate + carbamoyl phosphate = N-carbamoyl-L-aspartate + phosphate, the committed step of pyrimidine biosynthesis.
What genes are involved in aspartate carbamoyltransferase activity?
Key genes include CAD in mammals and pyrB/pyrI in E. coli, as well as regulators like PFKFB3.
How is aspartate carbamoyltransferase activity regulated?
It is regulated allosterically by nucleotides such as CTP and ATP, and by metal cations; in mammals, CAD is activated by PFKFB3 and mTOR signaling.
What diseases are associated with aspartate carbamoyltransferase activity?
Dysregulation is linked to cancer, where increased pyrimidine synthesis supports proliferation. Developmental roles have also been suggested.
How can I measure aspartate carbamoyltransferase activity?
HPLC-based assays and spectrophotometric methods are commonly used to quantify enzyme activity in tissues and cell extracts.
What is the role of ATCase in pyrimidine synthesis?
ATCase catalyzes the first committed step, producing N-carbamoyl-L-aspartate, which is subsequently converted to UMP.
Can CRISPR be used to study aspartate carbamoyltransferase activity?
Yes, CRISPR knockout, point mutation, knock-in, and overexpression models enable precise functional studies of ATCase-related genes.
What model organisms are used to study ATCase?
E. coli is a classic model for allosteric regulation, while mammalian cell lines and tissues are used for disease-related studies.
Is aspartate carbamoyltransferase activity tissue-specific?
Activity varies across tissues and developmental stages, as shown in rat liver and ovine tissues.
What are synonyms for aspartate carbamoyltransferase activity?
Common synonyms include ATCase activity, aspartate transcarbamoylase activity, and L-aspartate transcarbamylase activity.
Conclusion
GO:0004070, aspartate carbamoyltransferase activity, is a fundamental molecular function in pyrimidine biosynthesis with broad implications for cell growth, development, and disease. Its allosteric regulation and tissue-specific expression make it a compelling subject for biochemical and cancer research. By leveraging CRISPR-based models and advanced analytical methods, researchers can uncover new insights into ATCase regulation and its role in health and disease. EDITGENE offers the tools and expertise to accelerate these discoveries.
References
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