GO:0004641 phosphoribosylformylglycinamidine cyclo-ligase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0004641 (phosphoribosylformylglycinamidine cyclo-ligase activity) catalyzes the ATP-dependent cyclization of 2-(formamido)-N(1)-(5-phospho-D-ribosyl)acetamidine to 5-amino-1-(5-phospho-D-ribosyl)imidazole (AIR), a mid-pathway step in de novo purine biosynthesis.
• In humans, this activity is carried by the trifunctional enzyme GART (phosphoribosylglycinamide formyltransferase, phosphoribosylglycinamide synthetase, phosphoribosylaminoimidazole synthetase), which also performs GAR synthetase and GAR formyltransferase reactions.
• The enzyme is part of the purinosome, a dynamic metabolon of de novo purine biosynthetic enzymes that assembles in response to purine demand.
• GART expression and its non-canonical methyltransferase activity have been linked to tumor stemness and colorectal cancer progression.
• Post-translational modifications of de novo purine enzymes, including GART, provide an additional layer of pathway regulation.
• Loss or dysregulation of this activity impairs purine nucleotide supply, affecting DNA/RNA synthesis, cell proliferation, and intestinal barrier homeostasis.
Description
Phosphoribosylformylglycinamidine cyclo-ligase activity (GO:0004641) is a molecular function that catalyzes a key ATP-dependent cyclization step in the de novo purine biosynthetic pathway. The reaction converts 2-(formamido)-N(1)-(5-phospho-D-ribosyl)acetamidine into 5-amino-1-(5-phospho-D-ribosyl)imidazole (AIR), releasing ADP, phosphate, and protons. This step is essential for building the imidazole ring of the purine scaffold, which ultimately yields inosine monophosphate (IMP), the precursor of adenine and guanine nucleotides. In humans, this activity resides within the trifunctional GART polypeptide, which also carries GAR synthetase and GAR formyltransferase activities. Because purines are required for DNA replication, RNA transcription, and energy metabolism, the enzyme is central to cell proliferation and tissue homeostasis. Research on GO:0004641 spans structural enzymology, metabolon assembly, cancer metabolism, and inflammatory disease, making it a relevant target for both basic and translational studies.
phosphoribosylformylglycinamidine cyclo-ligase activity At A Glance
| GO ID | GO:0004641 |
|---|---|
| GO term | phosphoribosylformylglycinamidine cyclo-ligase activity |
| Ontology | molecular_function |
| Synonym | AIR synthase activity; AIR synthetase activity; 5'-aminoimidazole ribonucleotide synthetase activity; phosphoribosylaminoimidazole synthetase activity |
| Major function | ATP-dependent cyclization of 2-(formamido)-N(1)-(5-phospho-D-ribosyl)acetamidine to 5-amino-1-(5-phospho-D-ribosyl)imidazole (AIR) in de novo purine biosynthesis |
| Reaction | 2-(formamido)-N(1)-(5-phospho-D-ribosyl)acetamidine + ATP = 5-amino-1-(5-phospho-D-ribosyl)imidazole + ADP + 2 H+ + phosphate |
| Pathway context | De novo purine biosynthesis (IMP biosynthesis) |
| Human gene | GART (trifunctional enzyme) |
| Subcellular context | Cytosol; purinosome metabolon |
What Is GO:0004641?
GO:0004641 describes the catalytic activity that cyclizes 2-(formamido)-N(1)-(5-phospho-D-ribosyl)acetamidine to 5-amino-1-(5-phospho-D-ribosyl)imidazole using ATP, producing ADP, phosphate, and two protons. It is also known as AIR synthase or AIR synthetase activity and represents the fifth enzymatic step of de novo purine biosynthesis.
Why Is phosphoribosylformylglycinamidine cyclo-ligase activity Important in Cell Biology?
GO:0004641 is essential because it completes the imidazole ring of the purine nucleotide precursor AIR, a committed step toward IMP and all downstream purine nucleotides. Without this activity, cells cannot synthesize purines de novo, leading to proliferation arrest and metabolic stress. In humans, the activity is embedded in the multifunctional GART protein, whose structural and regulatory features have been resolved. GART is also a component of the purinosome, a dynamic metabolon that tunes pathway flux according to cellular purine demand. Beyond canonical metabolism, GART has been implicated in tumor stemness through a methyltransferase activity in the RUVBL1/β-catenin pathway, and its post-translational modifications contribute to pathway regulation. These features make GO:0004641 relevant to cancer biology, inflammatory disease, and metabolic engineering.
• Provides the AIR intermediate required for IMP and all purine nucleotides.
• Supports DNA replication and RNA synthesis in proliferating cells.
• Is part of the purinosome metabolon that channels pathway intermediates.
• GART, which carries this activity, is linked to colorectal cancer stemness.
• Post-translational modifications of GART and related enzymes modulate pathway flux.
• GART dysfunction is associated with intestinal barrier defects in colitis models.
• The activity is conserved from Drosophila to humans, enabling genetic studies.
• Bidirectional promoter coexpression with other purine genes supports coordinated regulation.
• Enzyme structure informs inhibitor design for purine-dependent cancers.
• Co-expression network analyses link purine pathway modules to dilated cardiomyopathy.
Molecular Mechanism of phosphoribosylformylglycinamidine cyclo-ligase activity
Substrate binding and ATP utilization
In simple terms: The enzyme grabs the formylated sugar intermediate and uses ATP as an energy source to close a ring.
The enzyme binds 2-(formamido)-N(1)-(5-phospho-D-ribosyl)acetamidine and ATP, positioning the substrate for an intramolecular cyclization that forms the imidazole ring of AIR. ATP hydrolysis provides the driving force, yielding ADP, phosphate, and protons. In humans, this step is catalyzed by the AIR synthetase domain of the trifunctional GART protein.
Cyclization chemistry
In simple terms: A new ring is formed inside the molecule, turning an open-chain intermediate into the purine building block AIR.
The reaction converts the formamido acetamidine moiety into the fused imidazole of 5-amino-1-(5-phospho-D-ribosyl)imidazole (AIR). This cyclization is a committed step toward IMP and is conserved across species, as shown by genetic studies in Drosophila where multiple purine activities map to a single locus.
Multifunctional enzyme architecture
In simple terms: In humans, the ring-closing activity is part of a larger enzyme that also performs two earlier steps.
Human GART is a trifunctional polypeptide carrying GAR synthetase, GAR formyltransferase, and AIR synthetase (GO:0004641) activities. Structural studies of human GART have revealed the domain organization that supports channeling of unstable intermediates.
Purinosome assembly and channeling
In simple terms: The enzyme can cluster with other purine enzymes into a temporary factory that speeds up the pathway.
De novo purine biosynthetic enzymes, including GART, assemble into a purinosome metabolon under purine-limiting conditions, as detected by fluorescence microscopy. This assembly is thought to enhance pathway efficiency by channeling intermediates.
Post-translational regulation
In simple terms: Chemical tags added to the enzyme can change how well it works.
Mapping of post-translational modifications on de novo purine biosynthetic enzymes, including GART, has revealed phosphorylation and other modifications that may regulate pathway activity. These modifications provide a layer of control beyond transcriptional regulation.
Key Genes Involved in GO:0004641 phosphoribosylformylglycinamidine cyclo-ligase activity
The following genes and proteins are directly or functionally associated with GO:0004641 and de novo purine biosynthesis.
| Gene | Major Role | Research Relevance |
|---|---|---|
| GART | Trifunctional enzyme carrying AIR synthetase (GO:0004641), GAR synthetase, and GAR formyltransferase activities | Structural and cancer studies; target for purine pathway inhibition |
| ATIC | Bifunctional enzyme in de novo purine biosynthesis (AICAR transformylase/IMP cyclohydrolase) | Purinosome component; pathway context |
| PAICS | Bifunctional enzyme (AIR carboxylase/SAICAR synthetase) acting downstream of AIR | Purinosome component; metabolon studies |
| ADSL | Adenylosuccinate lyase in purine biosynthesis | Purinosome component; pathway regulation |
| PPAT | Phosphoribosyl pyrophosphate amidotransferase, first step of de novo purine biosynthesis | Pathway initiation; purinosome assembly |
| PFAS | Phosphoribosylformylglycinamidine synthase, step preceding GO:0004641 | Provides substrate for AIR synthetase |
| GARS | Glycyl-tRNA synthetase; not to be confused with GAR synthetase activity of GART | Distinct gene; avoid confusion in literature searches |
| RUVBL1 | ATPase involved in chromatin remodeling and β-catenin signaling | Interacts with GART in cancer stemness pathway |
| CTNNB1 | β-catenin, transcriptional co-activator | Downstream of GART methyltransferase activity in colorectal cancer |
| TP53 | Tumor suppressor | Linked to GART-mediated p53/PUMA cascade in colitis |
| PUMA (BBC3) | Pro-apoptotic Bcl-2 family member | Effector of GART-p38/p53 signaling in intestinal epithelium |
| MAPK14 (p38) | Stress-activated kinase | Mediates GART-dependent intestinal barrier renewal |
| Drosophila Prat | Multifunctional purine locus in Drosophila | Genetic model for purine pathway enzyme clustering |
| Chicken GART | Avian GART coexpressed with other purine genes | Bidirectional promoter model for coordinated expression |
| HPRT1 | Salvage pathway enzyme | Contrasts with de novo pathway; relevant to purine homeostasis |
| IMPDH1/2 | IMP dehydrogenase, downstream of IMP | Links purine biosynthesis to GTP supply |
| GMPS | GMP synthase, downstream of IMP | Purine nucleotide end-product context |
| ADSS | Adenylosuccinate synthetase, downstream of IMP | Purine nucleotide end-product context |
How Is phosphoribosylformylglycinamidine cyclo-ligase activity Regulated?
GO:0004641 is regulated at multiple levels. Transcription of GART and neighboring purine genes can be coordinated through shared promoter elements, as shown for closely linked avian genes. Post-translational modifications of de novo purine enzymes, including GART, provide rapid modulation of activity. Purinosome assembly in response to purine demand represents a spatial regulatory mechanism that clusters GART with other pathway enzymes. In disease contexts, GART participates in signaling cascades such as p38/p53/PUMA in intestinal epithelium and RUVBL1/β-catenin in cancer stemness, indicating crosstalk between purine metabolism and cell signaling.
phosphoribosylformylglycinamidine cyclo-ligase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| GART | Colorectal cancer stemness via RUVBL1/β-catenin | GART knockout or point-mutation colorectal cancer cell lines; xenograft models |
| GART | Colitis and intestinal barrier dysfunction | Intestinal epithelial cell-specific Gart knockout mice; DSS colitis model |
| GART | Dilated cardiomyopathy (co-expression module) | Cardiomyocyte overexpression or knockout models; RNA-seq |
| GART | Purine biosynthesis defects (generic) | Patient-derived fibroblasts; CRISPR knock-in of patient variants |
| PFAS | Purine pathway disruption upstream of GO:0004641 | PFAS knockout cell lines; metabolomics |
Cancer and tumor stemness
GART, which carries GO:0004641 activity, has been shown to function as a methyltransferase in the RUVBL1/β-catenin signaling pathway, promoting tumor stemness in colorectal cancer. This suggests that purine biosynthetic enzymes can have non-canonical roles in oncogenesis beyond nucleotide supply.
Intestinal inflammation and barrier function
GART mediates renewal of the intestinal epithelial barrier via a p38/p53/PUMA cascade in colitis models, linking purine biosynthesis to epithelial homeostasis and apoptosis.
Cardiomyopathy and metabolic remodeling
Co-expression network analysis in human dilated cardiomyopathy has identified purine biosynthetic modules, including GART-associated pathways, suggesting a role in cardiac metabolic remodeling.
Developmental and genetic models
In Drosophila, multiple purine pathway enzyme activities are encoded at a single genetic locus, providing a model for studying the developmental consequences of purine pathway disruption.
From phosphoribosylformylglycinamidine cyclo-ligase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of GO:0004641 activity impair proliferation? | GART knockout cell lines (e.g., HCT116, HEK293T) with purine rescue |
| Does a specific GART point mutation alter catalysis? | CRISPR point-mutation knock-in of catalytic residues followed by enzyme assays |
| Can tagged GART be used to study purinosome assembly? | Endogenous knock-in of fluorescent tag (e.g., GFP) for live imaging |
| Does GART overexpression drive tumor stemness? | Doxycycline-inducible GART overexpression in colorectal cancer cells |
| How do post-translational modifications regulate GART? | Knock-in of phospho-null or phospho-mimetic mutations at modified residues |
| Is GART required for intestinal barrier renewal? | Conditional Gart knockout in mouse intestinal epithelium |
How to Study the phosphoribosylformylglycinamidine cyclo-ligase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Enzyme activity assay | AIR synthetase catalytic rate | Validation of GART variants and inhibitors |
| Fluorescence microscopy | Purinosome assembly and localization | Live-cell imaging of metabolon dynamics |
| Mass spectrometry proteomics | Post-translational modifications on GART | Mapping regulatory sites |
| RNA-seq / co-expression analysis | Transcriptional modules including GART | Disease association studies |
| CRISPR knockout screening | Fitness effects of GART loss | Cancer dependency studies |
| Metabolomics | Purine intermediate levels (AIR, IMP) | Pathway flux analysis |
| Western blot / immunoprecipitation | GART protein levels and interactions | Signaling pathway studies |
| Reporter assays | Promoter activity of GART and linked genes | Transcriptional regulation studies |
Enzymatic assays for GO:0004641
Direct measurement of AIR synthetase activity can be performed using coupled spectrophotometric or radiometric assays that monitor ATP consumption or AIR formation. Purified recombinant GART domains or full-length protein are used, and activity is validated against known substrates.
Fluorescence microscopy of purinosomes
Purinosome formation can be detected by tagging de novo purine enzymes, including GART, with fluorescent proteins and imaging their clustering under purine-limiting conditions.
Proteomics and PTM mapping
Mass spectrometry-based proteomics can map post-translational modifications on GART and other purine enzymes, revealing regulatory sites.
Co-expression and network analysis
RNA-seq and co-expression network analysis can identify modules linking GART and purine pathway genes to disease phenotypes such as dilated cardiomyopathy.
How CRISPR Can Be Used to Study GO:0004641 phosphoribosylformylglycinamidine cyclo-ligase activity
Knockout
CRISPR knockout of GART eliminates GO:0004641 activity, causing purine auxotrophy that can be rescued with exogenous purines. This model is useful for testing pathway dependency in cancer cell lines and for validating inhibitor specificity.
Point Mutation
Point mutations in the AIR synthetase domain of GART can be introduced to dissect catalytic residues and ATP-binding sites. Such knock-in models allow precise structure-function studies without confounding effects of full gene loss.
Knock-in
Knock-in of fluorescent or affinity tags at the endogenous GART locus enables live-cell imaging of purinosome assembly and proteomic isolation of GART complexes.
Overexpression
Overexpression of GART via CRISPR activation or inducible lentiviral systems can model the elevated purine biosynthesis observed in tumors and test its role in stemness and chemoresistance.
How EDITGENE Supports phosphoribosylformylglycinamidine cyclo-ligase activity Research
Researchers studying phosphoribosylformylglycinamidine cyclo-ligase activity-related genes often need to determine whether a candidate gene is causally involved in purine metabolism, cell proliferation, or disease. EDITGENE provides end-to-end CRISPR services to generate precisely engineered cell models for such studies.
Contact EDITGENE today to design your custom CRISPR model for phosphoribosylformylglycinamidine cyclo-ligase activity research.
Frequently Asked Questions About phosphoribosylformylglycinamidine cyclo-ligase activity
What is phosphoribosylformylglycinamidine cyclo-ligase activity?
It is the enzymatic activity (GO:0004641) that converts 2-(formamido)-N(1)-(5-phospho-D-ribosyl)acetamidine to 5-amino-1-(5-phospho-D-ribosyl)imidazole using ATP, a step in de novo purine biosynthesis.
What gene encodes phosphoribosylformylglycinamidine cyclo-ligase activity in humans?
In humans, this activity is carried by the trifunctional GART gene, which also encodes GAR synthetase and GAR formyltransferase activities.
What is another name for GO:0004641?
Common synonyms include AIR synthase activity, AIR synthetase activity, and phosphoribosylaminoimidazole synthetase activity.
What reaction does GO:0004641 catalyze?
It catalyzes the ATP-dependent cyclization of 2-(formamido)-N(1)-(5-phospho-D-ribosyl)acetamidine to 5-amino-1-(5-phospho-D-ribosyl)imidazole, producing ADP, phosphate, and protons.
Which pathway is GO:0004641 part of?
It is part of the de novo purine biosynthetic pathway leading to IMP.
Is GART involved in cancer?
Yes, GART has been shown to promote tumor stemness in colorectal cancer through a methyltransferase activity in the RUVBL1/β-catenin pathway.
How is GO:0004641 regulated?
It is regulated by transcriptional coexpression with neighboring purine genes, post-translational modifications, and purinosome assembly.
What diseases are linked to GART dysfunction?
GART has been linked to colorectal cancer, colitis-associated intestinal barrier defects, and co-expression modules in dilated cardiomyopathy.
What model systems are used to study GO:0004641?
Common models include human cancer cell lines with GART knockout or knock-in, Drosophila purine locus mutants, and mouse intestinal epithelium knockouts.
How can I study GO:0004641 with CRISPR?
CRISPR knockout, point mutation knock-in, tagged knock-in, and overexpression models can be generated to test the function of GART and its catalytic domain.
Conclusion
GO:0004641 (phosphoribosylformylglycinamidine cyclo-ligase activity) is a central enzymatic step in de novo purine biosynthesis, carried by the trifunctional GART protein in humans. Its role in purinosome assembly, post-translational regulation, and disease-associated signaling makes it a compelling target for metabolic and cancer research. Understanding its mechanism and regulation requires precise genetic models, which can be efficiently generated using CRISPR-based approaches.
References
- 1. Henikoff S et al.. 1986. Multiple purine pathway enzyme activities are encoded at a single genetic locus in Drosophila.. Proc Natl Acad Sci U S A 83(3):720-4 PMID: 3080748
- 2. Pedley AM et al.. 2018. Detecting Purinosome Metabolon Formation with Fluorescence Microscopy.. Methods Mol Biol 1764:279-289 PMID: 29605921
- 3. Welin M et al.. 2010. Structural studies of tri-functional human GART.. Nucleic Acids Res 38(20):7308-19 PMID: 20631005
- 4. Tang C et al.. 2023. GART Functions as a Novel Methyltransferase in the RUVBL1/β-Catenin Signaling Pathway to Promote Tumor Stemness in Colorectal Cancer.. Adv Sci (Weinh) 10(25):e2301264 PMID: 37439412
- 5. Liu C et al.. 2019. Mapping Post-Translational Modifications of de Novo Purine Biosynthetic Enzymes: Implications for Pathway Regulation.. J Proteome Res 18(5):2078-2087 PMID: 30964683
- 6. Xiao J et al.. 2020. Co-expression analysis provides important module and pathways of human dilated cardiomyopathy.. J Cell Physiol 235(1):494-503 PMID: 31236962
- 7. Bai JA et al.. 2016. GART mediates the renewal of intestinal epithelial barrier via p38/p53/PUMA cascade in colitis.. Apoptosis 21(12):1386-1397 PMID: 27718035
- 8. Gavalas A et al.. 1993. Coexpression of two closely linked avian genes for purine nucleotide synthesis from a bidirectional promoter.. Mol Cell Biol 13(8):4784-92 PMID: 8336716
