GO:0004644 phosphoribosylglycinamide formyltransferase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0004644 describes the enzymatic activity that transfers a formyl group from 10-formyltetrahydrofolate to N1-(5-phospho-D-ribosyl)glycinamide (GAR), producing N2-formyl-N1-(5-phospho-D-ribosyl)glycinamide (FGAR) and tetrahydrofolate.
• In humans, this activity is carried by the trifunctional GART protein, which also performs phosphoribosylamine-glycine ligase and phosphoribosylformylglycinamidine cyclo-ligase steps of de novo purine biosynthesis.
• GART is a key component of the purinosome, a dynamic metabolon that organizes purine biosynthetic enzymes for efficient pathway flux.
• Disruption of GART or its homologs affects nucleotide pools, inflammation, and antiviral resistance, linking GO:0004644 to host-pathogen interactions and immune signaling.
• Bacterial PurN, a homolog of the GART formyltransferase domain, contributes to antibiotic tolerance and virulence, making it a potential antibacterial target.
• Experimental models for studying GO:0004644 include knockout and point-mutation cell lines, tagged knock-ins for imaging, and overexpression systems for biochemical assays.
Description
Phosphoribosylglycinamide formyltransferase activity (GO:0004644) is a molecular function that catalyzes the transfer of a formyl group from 10-formyltetrahydrofolate to N1-(5-phospho-D-ribosyl)glycinamide (GAR), yielding N2-formyl-N1-(5-phospho-D-ribosyl)glycinamide (FGAR) and tetrahydrofolate. This reaction is the fourth step of the de novo purine biosynthesis pathway, a central metabolic route for the production of purine nucleotides. In humans, the activity resides within the trifunctional GART protein, which also catalyzes the second and third steps of the pathway, and is part of a larger purinosome complex. Because purine nucleotides are essential for DNA replication, RNA synthesis, and cellular energy metabolism, precise regulation of GO:0004644 is critical for cell proliferation and survival. Researchers study GO:0004644 to understand how cells coordinate nucleotide production under normal and stress conditions, and to identify vulnerabilities in diseases such as cancer and infections. The enzyme is conserved from bacteria to humans, and its bacterial homolog PurN has been implicated in antibiotic tolerance and virulence. In mammalian cells, mutations in GART can alter purine flux and have been linked to metabolic and inflammatory responses. The availability of recombinant human GART as a single domain has enabled detailed structural and kinetic studies. This article provides a research-grade overview of GO:0004644, covering its definition, mechanism, key genes, disease relevance, and experimental methods, with a focus on CRISPR-based models for functional interrogation.
phosphoribosylglycinamide formyltransferase activity At A Glance
| GO ID | GO:0004644 |
|---|---|
| GO term | phosphoribosylglycinamide formyltransferase activity |
| Ontology | molecular_function |
| Synonym | GAR transformylase activity; GART activity; 5'-phosphoribosylglycinamide transformylase activity; glycinamide ribonucleotide transformylase activity |
| Major function | Catalyzes the formylation of GAR to FGAR in de novo purine biosynthesis |
| Reaction | 10-formyltetrahydrofolate + N1-(5-phospho-D-ribosyl)glycinamide = tetrahydrofolate + N2-formyl-N1-(5-phospho-D-ribosyl)glycinamide |
| Cofactor | 10-formyltetrahydrofolate (folate derivative) |
| Pathway | De novo purine biosynthesis |
| Human gene | GART (trifunctional enzyme) |
What Is GO:0004644?
GO:0004644 is defined by QuickGO as the catalysis of the reaction: 10-formyltetrahydrofolate + N1-(5-phospho-D-ribosyl)glycinamide = tetrahydrofolate + N2-formyl-N1-(5-phospho-D-ribosyl)glycinamide. In simpler terms, it is the enzyme activity that adds a formyl group to GAR during purine biosynthesis, using 10-formyltetrahydrofolate as the formyl donor.
Why Is phosphoribosylglycinamide formyltransferase activity Important in Cell Biology?
GO:0004644 is essential for de novo purine biosynthesis, which supplies the nucleotides required for DNA and RNA synthesis, energy metabolism, and cell signaling. Dysregulation of this activity can lead to imbalances in purine pools, affecting cell proliferation and survival, and has been implicated in cancer, inflammation, and host-pathogen interactions. Understanding its mechanism and regulation provides opportunities for therapeutic intervention, particularly in diseases where purine metabolism is altered.
• Provides the fourth step of de novo purine biosynthesis, critical for nucleotide production.
• Human GART is a trifunctional enzyme; its formyltransferase domain carries GO:0004644.
• Part of the purinosome metabolon, which enhances pathway efficiency.
• Bacterial PurN homolog contributes to antibiotic tolerance and virulence.
• GART expression is induced after spinal cord injury and may modulate inflammation.
• Mutations in GART can alter purine synthesis and cellular metabolism.
• Gammaherpesvirus tegument proteins mimic FGARAT to disrupt host antiviral resistance.
• Target for anticancer and antibacterial drug development.
• Modeled in Drosophila where multiple purine enzymes are encoded at a single locus.
• Recombinant human GART enables biochemical and structural studies.
Molecular Mechanism of phosphoribosylglycinamide formyltransferase activity
Substrate Binding and Catalysis
In simple terms: The enzyme grabs GAR and a folate carrier, then moves a formyl group from the carrier to GAR.
The formyltransferase domain of GART binds N1-(5-phospho-D-ribosyl)glycinamide (GAR) and 10-formyltetrahydrofolate in a sequential ordered mechanism. Structural studies of human GART reveal a conserved fold that positions the formyl group for transfer to the GAR amino group, forming FGAR. The reaction releases tetrahydrofolate and FGAR, which proceeds to the next step of purine biosynthesis.
Role of the Trifunctional GART Protein
In simple terms: In humans, the enzyme is part of a larger protein that also does two other steps, making the process more efficient.
Human GART is a trifunctional polypeptide that catalyzes three consecutive steps of de novo purine biosynthesis: phosphoribosylamine-glycine ligase, phosphoribosylglycinamide formyltransferase (GO:0004644), and phosphoribosylformylglycinamidine cyclo-ligase. The formyltransferase activity resides in the C-terminal domain, while the other activities are in separate domains. This organization allows channeling of intermediates and may enhance pathway flux.
Purinosome Assembly and Metabolic Channeling
In simple terms: The enzyme gathers with other purine enzymes into a tiny factory called the purinosome to work more efficiently.
GART is a component of the purinosome, a dynamic multi-enzyme complex that forms under conditions of high purine demand. Fluorescence microscopy studies have shown that purinosome assembly correlates with increased de novo purine biosynthesis and can be modulated by cellular signals. This spatial organization may facilitate substrate channeling and protect intermediates.
Cofactor and Folate Metabolism
In simple terms: The enzyme needs a folate derivative to supply the formyl group.
10-formyltetrahydrofolate serves as the formyl donor for GO:0004644. Folate metabolism thus directly impacts the activity, and perturbations in folate pathways can affect purine synthesis. The reaction produces tetrahydrofolate, which is recycled in one-carbon metabolism.
Regulation by Cellular Demand
In simple terms: When cells need more purines, they can adjust the enzyme's activity or assembly.
Purine biosynthesis is regulated in response to cellular demand, and GART expression can be induced under certain conditions such as spinal cord injury. The purinosome assembly is dynamic and responds to changes in purine levels. Additionally, bacterial PurN is involved in antibiotic tolerance, suggesting regulation in response to stress.
Key Genes Involved in GO:0004644 phosphoribosylglycinamide formyltransferase activity
The following genes and proteins are directly or functionally linked to phosphoribosylglycinamide formyltransferase activity (GO:0004644).
| Gene | Major Role | Research Relevance |
|---|---|---|
| GART (human) | Trifunctional enzyme; formyltransferase domain carries GO:0004644 | Structural and kinetic studies; cancer metabolism |
| GART (Drosophila) | Encodes multiple purine pathway activities at a single locus | Genetic studies of purine biosynthesis |
| GART (Chinese hamster ovary) | De novo purine synthesis; mutations affect enzyme activity | Cell line models for purine auxotrophy |
| PurN (Staphylococcus aureus) | Bacterial homolog of GAR transformylase | Antibiotic tolerance and virulence |
| PurT (E. coli) | Alternative GAR transformylase using formate | Comparative enzymology (not directly cited here) |
| ATIC | Bifunctional enzyme in purine biosynthesis | Purinosome component |
| PPAT | First step of purine biosynthesis | Purinosome component |
| PFAS | FGAR amidotransferase | Purinosome component |
| PAICS | Bifunctional enzyme in purine biosynthesis | Purinosome component |
| ADSL | Adenylosuccinate lyase | Purinosome component |
| IMPDH | Inosine monophosphate dehydrogenase | Purine salvage and synthesis |
| MTHFD1 | One-carbon metabolism; supplies 10-formyltetrahydrofolate | Folate metabolism |
| SHMT | Serine hydroxymethyltransferase | One-carbon metabolism |
| GART (rat) | GART expression after spinal cord injury | Inflammation and injury response |
| Gammaherpesvirus FGARAT homolog | Mimics FGARAT to disrupt antiviral resistance | Host-pathogen interactions |
How Is phosphoribosylglycinamide formyltransferase activity Regulated?
The activity of phosphoribosylglycinamide formyltransferase is regulated at multiple levels. In mammalian cells, GART expression can be induced in response to injury, as shown in rat spinal cord where GART expression increases after injury and may modulate inflammation. The purinosome assembly is dynamic and responds to cellular purine demand, with fluorescence microscopy studies demonstrating that purinosome formation correlates with increased de novo purine biosynthesis. Additionally, bacterial PurN is involved in antibiotic tolerance, suggesting regulation under stress conditions. Folate availability also impacts the reaction, as 10-formyltetrahydrofolate is the formyl donor.
phosphoribosylglycinamide formyltransferase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| GART | Cancer cell proliferation | Knockout or point-mutation cancer cell lines |
| GART | Spinal cord injury and inflammation | Rat injury models with GART overexpression or knockdown |
| PurN | Antibiotic tolerance in S. aureus | Bacterial knockout and overexpression |
| GART | Purine metabolism disorders | Chinese hamster ovary cell mutants |
| Gammaherpesvirus FGARAT homolog | Viral evasion of antiviral resistance | Viral infection models with host GART knockout |
Cancer and Cell Proliferation
De novo purine biosynthesis is upregulated in many cancers to support rapid cell proliferation. GART, which carries GO:0004644, is a potential target for anticancer therapy, and inhibitors of the formyltransferase activity have been explored. The purinosome assembly is also a target for drug discovery.
Inflammation and Spinal Cord Injury
GART expression is increased in rat spinal cord after injury, and it may play a role in inflammation. This suggests that GO:0004644 could be involved in neuroinflammatory responses, though the exact mechanism requires further study.
Host-Pathogen Interactions
Gammaherpesvirus tegument proteins with homology to the FGARAT purine biosynthesis enzyme can disrupt host antiviral resistances. This highlights a role for purine biosynthetic enzymes, including GAR transformylase, in viral evasion of host immunity.
Bacterial Infections and Antibiotic Tolerance
In Staphylococcus aureus, PurN is involved in antibiotic tolerance and virulence. Targeting bacterial GAR transformylase could be a strategy to combat persistent infections.
From phosphoribosylglycinamide formyltransferase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| What is the effect of GART loss on purine pools? | GART knockout cell lines |
| How does a specific point mutation affect enzyme kinetics? | Point-mutation knock-in of GART |
| Where is GART localized in live cells? | Tagged knock-in with fluorescent protein |
| Does GART overexpression increase purine synthesis? | Overexpression cell lines |
| How does PurN contribute to antibiotic tolerance? | Bacterial PurN knockout and overexpression |
| What is the role of GART in inflammation after injury? | Rat spinal cord injury model with GART modulation |
How to Study the phosphoribosylglycinamide formyltransferase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Enzymatic assay | Formyltransferase activity | Kinetic studies and inhibitor screening |
| Fluorescence microscopy | Purinosome assembly | Live-cell imaging of GART clustering |
| qPCR/RNA-seq | GART mRNA expression | Transcriptional regulation after injury |
| Metabolomics | Purine metabolite levels | Pathway flux analysis |
| Western blot | GART protein levels | Expression analysis |
| CRISPR knockout | Loss of GART function | Phenotypic studies |
| CRISPR knock-in | Tagged GART | Localization and interaction studies |
| Bacterial genetics | PurN function | Antibiotic tolerance studies |
Enzymatic Assays
Direct measurement of GAR transformylase activity can be performed using recombinant human GART and spectrophotometric or radiometric assays that monitor the conversion of GAR to FGAR. These assays are useful for kinetic characterization and inhibitor screening.
Fluorescence Microscopy for Purinosome Detection
Purinosome formation can be visualized by tagging purine biosynthetic enzymes, including GART, with fluorescent proteins and imaging their clustering in live cells. This method reveals dynamic assembly in response to purine demand.
Gene Expression Analysis
Quantitative PCR and RNA-seq can measure GART mRNA levels in tissues or cells under various conditions, such as after spinal cord injury. This helps assess transcriptional regulation of GO:0004644.
Metabolomics
Mass spectrometry-based metabolomics can quantify purine intermediates and nucleotides to assess flux through the de novo pathway and the impact of GART perturbations.
How CRISPR Can Be Used to Study GO:0004644 phosphoribosylglycinamide formyltransferase activity
Knockout
CRISPR knockout of GART can be used to eliminate GO:0004644 activity and study its role in purine biosynthesis, cell proliferation, and disease models. Knockout cell lines may require exogenous purines for survival, demonstrating auxotrophy.
Point Mutation
Point mutations in the GART formyltransferase domain can be introduced to dissect catalytic residues and assess their impact on enzyme activity and cellular metabolism. Such models help validate structural predictions and identify pathogenic variants.
Knock-in
Knock-in of fluorescent or affinity tags into the endogenous GART locus allows real-time imaging of purinosome assembly and protein interactions without overexpression artifacts.
Overexpression
Overexpression of wild-type or mutant GART can be used to study gain-of-function effects, increase purine flux, and test drug sensitivity. This approach is useful for biochemical purification and structural studies.
How EDITGENE Supports phosphoribosylglycinamide formyltransferase activity Research
Researchers studying phosphoribosylglycinamide formyltransferase activity-related genes often need to determine whether a candidate gene is causally involved in purine metabolism, inflammation, or cancer. EDITGENE provides CRISPR-based services to create precise cell models for such investigations.
Contact EDITGENE today to design your custom CRISPR model for phosphoribosylglycinamide formyltransferase activity research.
Frequently Asked Questions About phosphoribosylglycinamide formyltransferase activity
What is phosphoribosylglycinamide formyltransferase activity?
It is the enzyme activity (GO:0004644) that transfers a formyl group from 10-formyltetrahydrofolate to GAR, forming FGAR in de novo purine biosynthesis.
What genes are involved in phosphoribosylglycinamide formyltransferase activity?
In humans, the GART gene encodes the trifunctional enzyme that carries this activity; bacterial homologs include PurN.
What is the role of GART in purine biosynthesis?
GART catalyzes three steps of de novo purine biosynthesis, including the formyltransferase step (GO:0004644).
How is phosphoribosylglycinamide formyltransferase activity regulated?
It is regulated by cellular purine demand, purinosome assembly, and folate availability, and can be induced after injury.
What diseases are associated with GART mutations?
GART mutations can affect purine metabolism and have been linked to cancer, inflammation, and host-pathogen interactions.
What is the purinosome?
The purinosome is a multi-enzyme complex that includes GART and other purine biosynthetic enzymes, enhancing pathway efficiency.
How can I study phosphoribosylglycinamide formyltransferase activity in the lab?
You can use enzymatic assays, fluorescence microscopy for purinosome detection, and CRISPR knockout or knock-in models.
What is the bacterial homolog of GAR transformylase?
PurN is the bacterial homolog, involved in antibiotic tolerance and virulence in Staphylococcus aureus.
Can CRISPR be used to study GO:0004644?
Yes, CRISPR knockout, point mutation, knock-in, and overexpression models can be used to dissect the function of GART and its formyltransferase activity.
What are the substrates of phosphoribosylglycinamide formyltransferase?
The substrates are 10-formyltetrahydrofolate and N1-(5-phospho-D-ribosyl)glycinamide (GAR).
Conclusion
Phosphoribosylglycinamide formyltransferase activity (GO:0004644) is a critical enzymatic step in de novo purine biosynthesis, carried by the trifunctional GART protein in humans and PurN in bacteria. Its role in nucleotide production, purinosome assembly, and disease-related pathways makes it a compelling target for research in cancer, inflammation, and infectious diseases. CRISPR-based models offer powerful tools to interrogate its function and regulation.
References
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- 2. Zhang D et al.. 2014. GART expression in rat spinal cord after injury and its role in inflammation.. Brain Res 1564:41-51 PMID: 24709117
- 3. Pedley AM et al.. 2018. Detecting Purinosome Metabolon Formation with Fluorescence Microscopy.. Methods Mol Biol 1764:279-289 PMID: 29605921
- 4. 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
- 5. Tsai K et al.. 2015. Disruption of host antiviral resistances by gammaherpesvirus tegument proteins with homology to the FGARAT purine biosynthesis enzyme.. Curr Opin Virol 14:30-40 PMID: 26256000
- 6. Welin M et al.. 2010. Structural studies of tri-functional human GART.. Nucleic Acids Res 38(20):7308-19 PMID: 20631005
- 7. Peng Q et al.. 2022. PurN Is Involved in Antibiotic Tolerance and Virulence in Staphylococcus aureus.. Antibiotics (Basel) 11(12) PMID: 36551359
- 8. Knox AJ et al.. 2009. Mutations in the Chinese hamster ovary cell GART gene of de novo purine synthesis.. Gene 429(1-2):23-30 PMID: 19007868
