GO:0004044 amidophosphoribosyltransferase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0004044 amidophosphoribosyltransferase activity catalyzes the committed step of de novo purine biosynthesis, converting 5-phospho-alpha-D-ribose 1-diphosphate (PRPP) and L-glutamine to 5-phospho-beta-D-ribosylamine, L-glutamate, and diphosphate.
• The enzyme is an oxygen-sensitive iron-sulfur protein in mammalian cells, and its activity is regulated by oxygen inactivation.
• Amidophosphoribosyltransferase activity increases in regenerating rat liver and after treatment with malotilate, linking it to de novo purine synthesis and cell proliferation.
• Nudix hydrolase 5 (NUDT5) has a non-enzymatic role in repressing purine de novo synthesis, indirectly affecting amidophosphoribosyltransferase activity.
• Yeast mutants affecting amidophosphoribosyltransferase activity provide genetic models for studying the enzyme's function and regulation.
• Studying GO:0004044 requires integrating biochemical assays, genetic models, and CRISPR-based editing to dissect its role in purine metabolism and disease.
Description
Amidophosphoribosyltransferase activity (GO:0004044) is a molecular function that catalyzes the first committed and rate-limiting step of de novo purine biosynthesis. This enzymatic reaction converts 5-phospho-alpha-D-ribose 1-diphosphate (PRPP) and L-glutamine into 5-phospho-beta-D-ribosylamine, L-glutamate, and diphosphate, thereby channeling carbon and nitrogen into the purine nucleotide pool. Because purines are essential for DNA and RNA synthesis, energy metabolism, and signaling, the regulation of this activity is critical for cell growth and proliferation. Researchers study amidophosphoribosyltransferase activity to understand how cells balance nucleotide supply with demand, and how dysregulation contributes to diseases such as cancer and metabolic disorders. The enzyme is also notable for its oxygen-sensitive iron-sulfur cluster in mammalian cells, which provides a unique mechanism for redox regulation of purine synthesis. This article integrates authoritative GO annotations with published literature to provide a comprehensive overview of the mechanism, genes, and research methods associated with GO:0004044.
amidophosphoribosyltransferase activity At A Glance
| GO ID | GO:0004044 |
|---|---|
| GO term | amidophosphoribosyltransferase activity |
| Ontology | molecular_function |
| Synonym | 5-phosphoribosyl-1-pyrophosphate amidotransferase activity; glutamine phosphoribosylpyrophosphate amidotransferase activity; phosphoribosyl pyrophosphate amidotransferase activity |
| Major function | Catalyzes the first committed step of de novo purine biosynthesis, converting PRPP and glutamine to phosphoribosylamine, glutamate, and diphosphate. |
| Cofactor | Iron-sulfur cluster; oxygen-sensitive in mammalian cells. |
| Regulation | Regulated by oxygen inactivation and increased in regenerating liver and after malotilate treatment. |
| Pathway | De novo purine biosynthesis (IMP biosynthesis). |
| Related gene | PPAT (human), ADE4 (yeast). |
What Is GO:0004044?
Amidophosphoribosyltransferase activity (GO:0004044) is defined as the catalysis of the reaction: 5-phospho-beta-D-ribosylamine + L-glutamate + diphosphate = 5-phospho-alpha-D-ribose 1-diphosphate + L-glutamine + H2O. In simpler terms, it is the enzyme activity that transfers an amide group from glutamine to PRPP, producing phosphoribosylamine, which is the first dedicated intermediate in purine biosynthesis. This activity is synonymous with glutamine phosphoribosylpyrophosphate amidotransferase and is essential for the de novo synthesis of purine nucleotides.
Why Is amidophosphoribosyltransferase activity Important in Cell Biology?
Amidophosphoribosyltransferase activity is critically important because it controls the flux of the entire de novo purine biosynthesis pathway, which supplies the nucleotides required for DNA replication, RNA transcription, and cellular energy metabolism. Dysregulation of this activity can lead to imbalances in purine pools, contributing to diseases such as cancer, where rapidly proliferating cells demand high levels of nucleotides. The oxygen-sensitive iron-sulfur cluster of mammalian amidophosphoribosyltransferase provides a unique link between cellular redox status and purine synthesis, making it a potential target for therapeutic intervention. Additionally, understanding this activity is essential for interpreting genetic disorders of purine metabolism and for developing drugs that modulate nucleotide synthesis.
• Controls the rate-limiting step of de novo purine biosynthesis, affecting DNA and RNA synthesis.
• Its activity is elevated in regenerating liver and proliferating cells, linking it to cell growth.
• The enzyme is an oxygen-sensitive iron-sulfur protein, connecting redox regulation to purine metabolism.
• NUDT5 represses purine de novo synthesis, indirectly influencing amidophosphoribosyltransferase activity.
• Mutations affecting amidophosphoribosyltransferase activity in yeast provide models for genetic studies.
• It is a potential target for anticancer and immunosuppressive therapies due to its role in nucleotide supply.
• Malotilate increases liver de novo purine synthesis and amidophosphoribosyltransferase activity, showing pharmacological modulation.
• Understanding its regulation can shed light on metabolic reprogramming in cancer and other diseases.
Molecular Mechanism of amidophosphoribosyltransferase activity
Substrate Binding and Catalysis
In simple terms: The enzyme grabs PRPP and glutamine and joins them to make a new molecule.
Amidophosphoribosyltransferase catalyzes the displacement of the pyrophosphate group of PRPP by the amide nitrogen of glutamine, yielding 5-phospho-beta-D-ribosylamine, glutamate, and diphosphate. This reaction is the committed step of purine biosynthesis and is highly regulated. The enzyme belongs to the amidotransferase family and requires the formation of a glutamine-binding site and a PRPP-binding site for catalysis.
Iron-Sulfur Cluster and Oxygen Sensitivity
In simple terms: The enzyme contains an iron-sulfur cluster that can be damaged by oxygen, turning it off.
Human amidophosphoribosyltransferase is an oxygen-sensitive iron-sulfur protein. The iron-sulfur cluster is essential for activity, and exposure to oxygen leads to inactivation, suggesting a regulatory role for oxygen in purine synthesis. This property distinguishes mammalian amidophosphoribosyltransferase from bacterial and yeast counterparts, which may lack such sensitivity.
Regulation by Metabolites and Redox State
In simple terms: The enzyme's activity can be turned up or down by cellular conditions like oxygen levels and metabolites.
Amidophosphoribosyltransferase activity is regulated by feedback inhibition by purine nucleotides and by oxygen inactivation. In regenerating rat liver, the activity increases, correlating with elevated PRPP concentrations and enhanced de novo purine synthesis. Malotilate treatment also increases liver de novo purine synthesis and amidophosphoribosyltransferase activity, indicating pharmacological regulation.
Role of NUDT5 in Repressing Purine Synthesis
In simple terms: A protein called NUDT5 can put a brake on purine synthesis, affecting the enzyme indirectly.
Nudix hydrolase 5 (NUDT5) has a non-enzymatic role in repressing purine de novo synthesis. This repression indirectly impacts amidophosphoribosyltransferase activity by limiting the supply of PRPP or by altering the expression of purine biosynthetic genes. The study highlights a novel regulatory layer in purine metabolism that could be targeted in cancer.
Genetic Models and Mutants
In simple terms: Yeast mutants with altered enzyme activity help scientists understand how the enzyme works.
Studies on Saccharomyces cerevisiae mutants affecting amidophosphoribosyltransferase activity have provided insights into the enzyme's function and regulation. These mutants display altered purine metabolism and growth phenotypes, making them valuable tools for genetic and biochemical analyses.
Key Genes Involved in GO:0004044 amidophosphoribosyltransferase activity
The following genes and proteins are directly or indirectly involved in amidophosphoribosyltransferase activity and its regulation.
| Gene | Major Role | Research Relevance |
|---|---|---|
| PPAT | Encodes amidophosphoribosyltransferase, the enzyme catalyzing the committed step of purine biosynthesis. | Target for studying purine metabolism and cancer; knockout models affect cell proliferation. |
| NUDT5 | Represses purine de novo synthesis via a non-enzymatic role. | Potential therapeutic target; knockdown increases purine synthesis. |
| ADE4 | Yeast homolog of PPAT; mutants affect amidophosphoribosyltransferase activity. | Model for genetic studies of purine biosynthesis. |
| PRPS1 | Produces PRPP, the substrate for amidophosphoribosyltransferase. | Mutations cause PRPP synthetase superactivity and gout. |
| GART | Involved in purine biosynthesis downstream of amidophosphoribosyltransferase. | Component of purinosome; studied for channeling. |
| ATIC | Catalyzes the final steps of purine biosynthesis. | Mutations cause AICA-ribosiduria. |
| IMPDH1 | Catalyzes IMP dehydrogenase step in guanine synthesis. | Target of immunosuppressive drugs. |
| IMPDH2 | Catalyzes IMP dehydrogenase step in guanine synthesis. | Overexpressed in cancer. |
| HPRT1 | Salvage enzyme for purine recycling. | Deficiency causes Lesch-Nyhan syndrome. |
| APRT | Salvage enzyme for adenine. | Deficiency causes kidney stones. |
| PPAT (bacterial) | Bacterial amidophosphoribosyltransferase. | Antibiotic target. |
| PPAT (plant) | Plant amidophosphoribosyltransferase. | Herbicide target. |
| NUDT5 (variant) | Non-enzymatic repressor of purine synthesis. | Studied in cancer metabolism. |
| MYC | Oncogene that upregulates purine biosynthesis genes. | Drives proliferation; linked to NUDT5 repression. |
| mTOR | Signaling pathway that promotes purine synthesis. | Inhibitors reduce amidophosphoribosyltransferase activity. |
| ATF4 | Transcription factor regulating amino acid and purine metabolism. | Integrated stress response links to purine synthesis. |
How Is amidophosphoribosyltransferase activity Regulated?
Amidophosphoribosyltransferase activity is regulated at multiple levels. In mammalian cells, the enzyme is inactivated by oxygen, likely through disruption of its iron-sulfur cluster, providing a redox-sensitive switch for purine synthesis. Feedback inhibition by purine nucleotides, such as AMP, GMP, and IMP, controls flux through the pathway. Hormonal and nutritional signals also influence activity; for example, malotilate treatment increases liver de novo purine synthesis and amidophosphoribosyltransferase activity. In regenerating rat liver, increased activity correlates with elevated PRPP concentrations, suggesting substrate availability as a regulatory factor. Additionally, NUDT5 represses purine de novo synthesis, indirectly affecting amidophosphoribosyltransferase activity. The mTOR pathway and oncogenes like MYC can upregulate purine biosynthesis, including amidophosphoribosyltransferase, to support proliferation.
amidophosphoribosyltransferase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| PPAT | Cancer; purine overproduction | Knockout or knockdown in cancer cell lines; xenograft models. |
| NUDT5 | Cancer; repression of purine synthesis | Overexpression and knockout models to study purine flux. |
| PRPS1 | Gout; PRPP synthetase superactivity | Point mutation knock-in in cell lines. |
| HPRT1 | Lesch-Nyhan syndrome | Knockout mice and patient-derived cells. |
| ATIC | AICA-ribosiduria | Knockout cell models. |
Cancer and Purine Metabolism
Rapidly proliferating cancer cells require high levels of purine nucleotides for DNA and RNA synthesis. Amidophosphoribosyltransferase activity is often upregulated in cancer to meet this demand. Oncogenes such as MYC drive the expression of purine biosynthetic genes, and NUDT5 repression of purine synthesis is a mechanism that can be overcome in cancer. Targeting amidophosphoribosyltransferase activity is a potential therapeutic strategy, as inhibition could starve cancer cells of nucleotides.
Metabolic Disorders and Gout
Overactivity of purine biosynthesis can lead to hyperuricemia and gout. Mutations in PRPS1, which supplies PRPP for amidophosphoribosyltransferase, cause PRPP synthetase superactivity and gout. Although direct mutations in PPAT are rare, dysregulation of its activity could contribute to purine overproduction. Understanding the regulation of amidophosphoribosyltransferase activity may offer new approaches for managing gout and related disorders.
Neurological and Developmental Disorders
Defects in purine metabolism can affect the nervous system, as seen in Lesch-Nyhan syndrome (HPRT1 deficiency) and AICA-ribosiduria (ATIC deficiency). While amidophosphoribosyltransferase activity is not directly linked to these disorders, its role in providing purines for brain development and function suggests that its dysregulation could contribute to neurological phenotypes. Further research is needed to establish direct connections.
From amidophosphoribosyltransferase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| What is the effect of PPAT knockout on cell proliferation? | CRISPR knockout in cancer cell lines (e.g., HeLa, HEK293). |
| How does oxygen sensitivity regulate amidophosphoribosyltransferase activity? | Point mutations in iron-sulfur cluster ligands; oxygen exposure assays. |
| Can a tagged PPAT be used to study localization? | Knock-in of fluorescent or epitope tags at the endogenous locus. |
| What is the impact of PPAT overexpression on purine pools? | Overexpression via lentiviral transduction in cell lines. |
| How does NUDT5 repression affect purine synthesis? | NUDT5 knockout or knockdown with metabolic profiling. |
| Do yeast ADE4 mutants mimic human disease? | Yeast genetic models with ADE4 mutations. |
How to Study the amidophosphoribosyltransferase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Enzyme activity assay | Catalytic conversion of PRPP and glutamine to phosphoribosylamine. | Kinetic studies and inhibitor screening. |
| Metabolomics | Intracellular purine nucleotide levels. | Assessing pathway flux in cells. |
| Stable isotope tracing | Flux through de novo purine synthesis. | Quantifying amidophosphoribosyltransferase activity in vivo. |
| CRISPR knockout screening | Genes affecting purine synthesis or cell growth. | Identifying regulators like NUDT5. |
| Western blot | Protein expression levels of PPAT and related enzymes. | Validating knockout or overexpression. |
| Immunofluorescence | Subcellular localization of PPAT. | Studying purinosome formation. |
| X-ray crystallography | Three-dimensional structure of the enzyme. | Structure-based drug design. |
| RNA-seq | Transcriptional changes in purine pathway genes. | Evaluating cellular response to metabolic stress. |
Biochemical Assays for Amidophosphoribosyltransferase Activity
Direct measurement of amidophosphoribosyltransferase activity is performed using radiolabeled substrates or by coupling the reaction to glutamate dehydrogenase and monitoring NADH production. These assays are essential for validating enzyme kinetics and inhibition.
Metabolic Profiling and Flux Analysis
Metabolomics and flux analysis using stable isotopes (e.g., 15N-glutamine) can quantify purine nucleotide pools and pathway flux, revealing changes in amidophosphoribosyltransferase activity in response to genetic or pharmacological perturbations.
Genetic Screens and CRISPR Libraries
CRISPR knockout libraries can be used to identify genes that modulate amidophosphoribosyltransferase activity or purine synthesis, such as NUDT5. These screens are powerful for discovering novel regulators and therapeutic targets.
Structural and Biophysical Studies
X-ray crystallography, NMR, and mass spectrometry can elucidate the structure of amidophosphoribosyltransferase, including its iron-sulfur cluster, and reveal conformational changes during catalysis. These methods inform drug design.
How CRISPR Can Be Used to Study GO:0004044 amidophosphoribosyltransferase activity
Knockout
CRISPR knockout of PPAT (encoding amidophosphoribosyltransferase) can be used to study the consequences of losing de novo purine synthesis. Cells with PPAT knockout are expected to require exogenous purines for growth, making them a model for purine auxotrophy. Such models can reveal compensatory pathways and drug sensitivities.
Point Mutation
Point mutations in the iron-sulfur cluster ligands of PPAT can be introduced to dissect the role of oxygen sensitivity in regulating amidophosphoribosyltransferase activity. These mutants can be used to test hypotheses about redox regulation and its impact on purine synthesis.
Knock-in
Knock-in of epitope tags (e.g., FLAG, HA) or fluorescent proteins at the endogenous PPAT locus allows for real-time imaging and proteomic analysis of the enzyme. This approach preserves endogenous regulation and can be used to study protein interactions and localization.
Overexpression
Overexpression of wild-type or mutant PPAT via lentiviral vectors can be used to study the effects of increased amidophosphoribosyltransferase activity on purine pools, cell proliferation, and drug resistance. This is particularly useful for modeling conditions of purine overproduction.
How EDITGENE Supports amidophosphoribosyltransferase activity Research
Researchers studying amidophosphoribosyltransferase activity-related genes often need to determine whether a candidate gene is causally involved in purine metabolism, cell proliferation, or disease. EDITGENE provides a comprehensive suite of CRISPR-based services to enable precise genetic manipulation and functional interrogation of these genes.
Contact EDITGENE today to design your custom CRISPR model for amidophosphoribosyltransferase activity research.
Related Products
| Product name | Cat.No. | Species | Gene ID |
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Frequently Asked Questions About amidophosphoribosyltransferase activity
What is amidophosphoribosyltransferase activity?
Amidophosphoribosyltransferase activity (GO:0004044) is the enzyme activity that catalyzes the first committed step of de novo purine biosynthesis, converting PRPP and glutamine to phosphoribosylamine, glutamate, and diphosphate.
What genes are involved in amidophosphoribosyltransferase activity?
The primary gene is PPAT, which encodes the enzyme. Other genes such as NUDT5, PRPS1, and ADE4 (yeast) also influence this activity.
What is the role of amidophosphoribosyltransferase in purine synthesis?
It catalyzes the rate-limiting step that commits PRPP to purine biosynthesis, making it a key control point for nucleotide production.
How is amidophosphoribosyltransferase activity regulated?
It is regulated by feedback inhibition by purine nucleotides, oxygen inactivation via its iron-sulfur cluster, and signals such as mTOR and NUDT5.
What diseases are associated with amidophosphoribosyltransferase activity?
Dysregulation is linked to cancer and metabolic disorders like gout, though direct mutations are rare.
What is the iron-sulfur cluster in amidophosphoribosyltransferase?
It is a cofactor essential for activity that renders the human enzyme oxygen-sensitive, providing a redox regulatory mechanism.
How can I study amidophosphoribosyltransferase activity in the lab?
Biochemical assays, metabolomics, CRISPR knockout/knock-in models, and structural studies are common approaches.
What model organisms are used for amidophosphoribosyltransferase research?
Saccharomyces cerevisiae (yeast) with ADE4 mutations and mammalian cell lines are widely used.
Can CRISPR be used to edit PPAT?
Yes, CRISPR knockout, point mutation, and knock-in strategies are effective for studying PPAT function.
What are the synonyms for amidophosphoribosyltransferase activity?
Synonyms include glutamine phosphoribosylpyrophosphate amidotransferase activity and phosphoribosyl pyrophosphate amidotransferase activity.
Conclusion
Amidophosphoribosyltransferase activity (GO:0004044) is a fundamental molecular function that governs the first committed step of de novo purine biosynthesis. Its regulation by oxygen, metabolites, and signaling pathways makes it a critical node in cellular metabolism, with implications for cancer, gout, and other diseases. Continued research using CRISPR models, biochemical assays, and metabolic profiling will deepen our understanding of this enzyme and its potential as a therapeutic target.
References
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- 2. Leff RL et al.. 1984. A possible role for oxygen inactivation in the regulation of amidophosphoribosyltransferase activity in mammalian cells.. Adv Enzyme Regul 22:403-11 PMID: 6382955
- 3. Nguyen TA et al.. 2025. A non-enzymatic role of Nudix hydrolase 5 in repressing purine de novo synthesis.. Science 390(6778):1143-1150 PMID: 41196952
- 4. Iwahana H et al.. 1996. [Amidophosphoribosyltransferase].. Nihon Rinsho 54(12):3202-6 PMID: 8976092
- 5. Itakura M et al.. 1979. Human amidophosphoribosyltransferase. An oxygen-sensitive iron-sulfur protein.. J Biol Chem 254(2):333-8 PMID: 762062
- 6. Itakura M et al.. 1986. Malotilate (diisopropyl 1,3-dithiol-2-ylidenemalonate) increases liver de novo purine synthesis and amidophosphoribosyltransferase activity.. J Pharmacol Exp Ther 237(3):794-8 PMID: 3012070
- 7. Itakura M et al.. 1986. Increase of amidophosphoribosyltransferase activity and phosphoribosylpyrophosphate concentration as the basis for increased de novo purine biosynthesis in the regenerating rat liver.. Adv Exp Med Biol 195 Pt B:347-55 PMID: 2429508
- 8. Nieto DJ et al.. 1983. Studies on mutants affecting amidophosphoribosyltransferase activity in Saccharomyces cerevisiae.. Can J Microbiol 29(6):681-8 PMID: 6349762
