GO:0004850 uridine phosphorylase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0004850 (uridine phosphorylase activity) catalyzes the reversible phosphorolysis of uridine to uracil and alpha-D-ribose 1-phosphate, a central step in pyrimidine salvage and ribose recycling.
• The reaction supplies ribose-1-phosphate for glycolysis and nucleotide synthesis when glucose is limited, supporting cancer cell survival.
• Uridine phosphorylase activity is circadian-regulated in liver, with enzyme activity and plasma uridine levels fluctuating over the daily cycle.
• Inhibiting uridine phosphorylase can modulate the antitumor activity of fluoropyrimidine prodrugs such as 5'-deoxy-5-fluorouridine.
• Uridine availability, which depends on uridine phosphorylase activity, influences macrophage ferroptosis and sepsis-induced acute lung injury.
• Altered pyrimidine salvage and uridine phosphorylase activity are linked to glioma progression and mitochondrial energy metabolism.
Description
Uridine phosphorylase activity (GO:0004850) is a molecular function that catalyzes the reversible conversion of uridine and phosphate into uracil and alpha-D-ribose 1-phosphate. This reaction sits at the intersection of pyrimidine salvage and ribose metabolism, allowing cells to recycle uridine for nucleotide synthesis or to liberate ribose-1-phosphate for energy-producing pathways. Because uridine phosphorylase activity determines the balance between uridine and uracil, it directly affects the availability of pyrimidine nucleosides for RNA and DNA synthesis, as well as the efficacy of nucleoside analog drugs. Researchers study this activity to understand how cells adapt to nutrient limitation, how circadian rhythms influence nucleotide pools, and how tumors exploit salvage pathways for growth. In addition, uridine phosphorylase activity has been detected in isolated plasma membranes of rat liver, suggesting that the enzyme may have compartment-specific roles beyond the cytosol. The importance of this activity extends to disease contexts: modulating uridine levels through uridine phosphorylase can influence ferroptosis in macrophages during sepsis-induced acute lung injury, and uridine-derived ribose fuels pancreatic cancer under glucose-restricted conditions. Consequently, GO:0004850 is a key target for metabolic, pharmacological, and CRISPR-based investigations.
uridine phosphorylase activity At A Glance
| GO ID | GO:0004850 |
|---|---|
| GO term | uridine phosphorylase activity |
| Ontology | molecular_function |
| Synonym | pyrimidine phosphorylase activity; UPase activity; UPH; UrdPase activity; uridine:phosphate alpha-D-ribosyltransferase activity |
| Definition | Catalysis of the reaction: uridine + phosphate = uracil + alpha-D-ribose 1-phosphate. |
| Major function | Pyrimidine salvage and ribose-1-phosphate generation |
| Reaction direction | Reversible phosphorolysis |
| Substrates | Uridine and phosphate |
| Products | Uracil and alpha-D-ribose 1-phosphate |
| Related pathways | Pyrimidine metabolism, nucleotide salvage, ribose recycling |
What Is GO:0004850?
Uridine phosphorylase activity (GO:0004850) is defined as the catalysis of the reaction: uridine + phosphate = uracil + alpha-D-ribose 1-phosphate. In other words, it is the enzyme activity that breaks the glycosidic bond of uridine in the presence of inorganic phosphate, yielding uracil and alpha-D-ribose 1-phosphate. This is a phosphorolysis reaction, not a simple hydrolysis, and it is reversible, so the same activity can also synthesize uridine from uracil and alpha-D-ribose 1-phosphate when conditions favor that direction. The activity is synonymous with pyrimidine phosphorylase activity, UPase activity, UPH, UrdPase activity, and uridine:phosphate alpha-D-ribosyltransferase activity.
Why Is uridine phosphorylase activity Important in Cell Biology?
Uridine phosphorylase activity is important because it controls the cellular balance between uridine and uracil, thereby influencing pyrimidine salvage, RNA synthesis, and the availability of ribose-1-phosphate for glycolysis and nucleotide production. This activity supports cancer cell proliferation under nutrient-limited conditions, modulates the response to fluoropyrimidine drugs, and is subject to circadian regulation that affects plasma uridine levels. Moreover, uridine availability downstream of this activity can influence ferroptosis and inflammatory injury in macrophages, linking pyrimidine metabolism to acute lung injury. Understanding GO:0004850 is therefore essential for metabolic research, drug development, and the design of CRISPR models that probe pyrimidine salvage in health and disease.
• Provides alpha-D-ribose 1-phosphate for glycolysis and nucleotide synthesis when glucose is scarce.
• Regulates uridine and uracil pools that are critical for RNA and DNA precursor supply.
• Modulates the antitumor activity of 5'-deoxy-5-fluorouridine and other fluoropyrimidine prodrugs.
• Shows circadian rhythmicity in liver, affecting plasma uridine concentrations.
• Influences macrophage ferroptosis and sepsis-induced acute lung injury through uridine availability.
• Is linked to glioma progression and patient survival through DNA methylation patterns.
• Contributes to mitochondrial energy metabolism and nucleotide homeostasis.
• Can be detected in plasma membranes, suggesting compartmentalized functions.
• Represents a potential target for metabolic therapy in pancreatic cancer.
• Enables CRISPR-based dissection of pyrimidine salvage pathways in diverse cell models.
What Happens During uridine phosphorylase activity?
Substrate binding and phosphorolysis
In simple terms: The enzyme grabs uridine and a phosphate molecule, then splits uridine into two pieces.
Uridine phosphorylase binds uridine and inorganic phosphate in its active site. The reaction proceeds via phosphorolysis, in which the phosphate attacks the glycosidic bond, releasing uracil and alpha-D-ribose 1-phosphate. This step is reversible, so the enzyme can also catalyze the reverse reaction to form uridine from uracil and alpha-D-ribose 1-phosphate when substrate conditions favor synthesis.
Product release and metabolic fate
In simple terms: After the split, the two products go their separate ways to be used by the cell.
The products, uracil and alpha-D-ribose 1-phosphate, are released from the active site. Uracil can be further degraded or salvaged, while alpha-D-ribose 1-phosphate enters glycolysis or nucleotide synthesis pathways. In glucose-restricted conditions, uridine-derived ribose becomes a key fuel for pancreatic cancer cells, highlighting the metabolic importance of this release step.
Role in pyrimidine salvage
In simple terms: This activity is part of the recycling system that turns old nucleosides back into useful building blocks.
Uridine phosphorylase activity is a core component of the pyrimidine salvage pathway. By converting uridine to uracil, it provides uracil for subsequent conversion to other pyrimidines, and by generating alpha-D-ribose 1-phosphate, it supplies ribose for nucleotide synthesis. This salvage function is particularly important in tissues with high nucleotide demand, such as tumors.
Circadian and physiological regulation
In simple terms: The body's clock can change how active this enzyme is at different times of day.
Hepatic uridine phosphorylase activity exhibits a circadian rhythm in mice, with enzyme activity and plasma uridine concentrations fluctuating over the 24-hour cycle. This regulation suggests that uridine phosphorylase activity is integrated into systemic metabolic timing, influencing when uridine is available for salvage or degradation.
Pharmacological relevance
In simple terms: Drugs that need this enzyme to work can be affected by how active it is.
Uridine phosphorylase activity is required for the activation of 5'-deoxy-5-fluorouridine, an antitumor prodrug. Inhibiting or modulating this activity can alter the drug's efficacy, making uridine phosphorylase a target for pharmacologic intervention.
Key Genes Involved in GO:0004850 uridine phosphorylase activity
The genes and proteins below are directly or indirectly associated with uridine phosphorylase activity (GO:0004850) and its metabolic context.
| Gene | Major Role | Research Relevance |
|---|---|---|
| UPP1 | Encodes uridine phosphorylase 1, the primary enzyme for GO:0004850 | Target for knockout and overexpression studies in pyrimidine salvage |
| UPP2 | Encodes uridine phosphorylase 2, a related enzyme with tissue-specific expression | Potential compensatory or distinct roles in uridine metabolism |
| UCK1 | Uridine-cytidine kinase 1, phosphorylates uridine to UMP | Links uridine salvage to nucleotide synthesis |
| UCK2 | Uridine-cytidine kinase 2, mitochondrial isoform | May influence mitochondrial ribose metabolism |
| PYNP | Pyrimidine nucleoside phosphorylase, broader activity | Related enzyme for comparative studies |
| DPYD | Dihydropyrimidine dehydrogenase, degrades uracil | Affects uracil pools downstream of GO:0004850 |
| TYMP | Thymidine phosphorylase, related pyrimidine salvage enzyme | Shares substrates and inhibitors with uridine phosphorylase |
| SLC29A1 | Equilibrative nucleoside transporter 1, imports uridine | Regulates substrate availability for GO:0004850 |
| SLC29A2 | Equilibrative nucleoside transporter 2 | Alternative uridine transport |
| SLC28A1 | Concentrative nucleoside transporter 1 | Uridine uptake in specific tissues |
| NT5C | Cytosolic 5'-nucleotidase, produces uridine from UMP | Supplies substrate for uridine phosphorylase |
| PNP | Purine nucleoside phosphorylase, related enzyme | Comparative studies of nucleoside phosphorylases |
| MIC19 | Mitochondrial cristae organizing protein, alters nucleotide metabolism | Links mitochondrial function to uridine metabolism |
| GPX4 | Glutathione peroxidase 4, ferroptosis regulator | Uridine availability affects ferroptosis in macrophages |
| ACSL4 | Acyl-CoA synthetase long-chain family member 4, ferroptosis promoter | Modulated by uridine in sepsis models |
| HIF1A | Hypoxia-inducible factor 1 alpha, metabolic regulator | May influence uridine salvage under hypoxia |
| MYC | Oncogene driving nucleotide synthesis | Potential link to uridine phosphorylase expression in cancer |
How Is uridine phosphorylase activity Regulated?
Uridine phosphorylase activity is regulated at multiple levels. In mouse liver, enzyme activity follows a circadian rhythm, with peak activity correlating with changes in plasma uridine concentration. This suggests that the activity is under control of the circadian clock and systemic metabolic cues. Additionally, substrate availability through nucleoside transporters and upstream nucleotidases can influence flux through the reaction. In cancer cells, uridine phosphorylase activity may be upregulated to support ribose supply under glucose limitation, potentially through metabolic stress signaling. Pharmacological inhibitors can also modulate the activity, as shown for fluoropyrimidine prodrug activation.
uridine phosphorylase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| UPP1 | Pancreatic cancer metabolism | UPP1 knockout in pancreatic cancer cell lines |
| UPP1 | Sepsis-induced acute lung injury | Macrophage-specific UPP1 knockout in mouse models |
| UPP1 | Glioma progression | UPP1 knockdown in glioma cells with methylation profiling |
| MIC19 | Mitochondrial energy metabolism | MIC19 knockout in liver cells |
| TYMP | Fluoropyrimidine drug response | TYMP overexpression in cancer cells treated with 5'-deoxy-5-fluorouridine |
Uridine phosphorylase activity in cancer metabolism
Uridine-derived ribose fuels glucose-restricted pancreatic cancer, and uridine phosphorylase activity is essential for this process. In gliomas, DNA methylation patterns associated with pyrimidine metabolism genes can predict patient survival, suggesting that uridine phosphorylase activity contributes to tumor progression. Targeting this activity may disrupt nucleotide supply in tumors that rely on salvage pathways.
Uridine phosphorylase activity and sepsis-induced acute lung injury
Uridine alleviates sepsis-induced acute lung injury by inhibiting ferroptosis of macrophages. Since uridine phosphorylase activity degrades uridine, modulating this activity could influence uridine availability and ferroptosis sensitivity in inflammatory diseases.
Uridine phosphorylase activity in mitochondrial and metabolic disorders
The mitochondrial cristae organizing protein MIC19 promotes energy expenditure by altering nucleotide metabolism, including uridine-related pathways. This links uridine phosphorylase activity to mitochondrial function and whole-body energy homeostasis.
Pharmacological implications of uridine phosphorylase activity
Uridine phosphorylase activity is required for the antitumor activity of 5'-deoxy-5-fluorouridine, and inhibitors of this enzyme can modulate drug efficacy. This makes GO:0004850 a target for improving fluoropyrimidine-based chemotherapy.
From uridine phosphorylase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does UPP1 loss alter uridine salvage? | UPP1 knockout cell line |
| Does a point mutation in the active site abolish enzyme activity? | Point-mutation knock-in of catalytic residues |
| Can tagged UPP1 reveal subcellular localization? | Tagged knock-in (e.g., GFP or FLAG) |
| Does UPP1 overexpression increase ribose supply? | UPP1 overexpression stable cell line |
| Which genes compensate for UPP1 loss? | CRISPR library screening in UPP1 knockout background |
| Does UPP1 modulation affect ferroptosis? | Macrophage knockout with ferroptosis inducers |
How to Study the uridine phosphorylase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| HPLC-based enzyme assay | Uridine phosphorylase activity | Validation of knockout or inhibitor effects |
| LC-MS metabolomics | Uridine, uracil, ribose-1-phosphate levels | Metabolic profiling of CRISPR models |
| RNA-seq | Gene expression changes | Pathway analysis in UPP1-altered cells |
| DNA methylation profiling | Epigenetic regulation of pyrimidine genes | Glioma progression studies |
| Isotope tracing | Flux through uridine salvage | Ribose recycling in cancer cells |
| Western blot | Protein expression of UPP1 | Overexpression and knockout validation |
| Immunofluorescence | Subcellular localization | Tagged knock-in models |
| CRISPR library screening | Genes affecting uridine dependence | Identification of synthetic lethal partners |
Enzymatic activity assays
Uridine phosphorylase activity can be measured using spectrophotometric or HPLC-based assays that monitor the conversion of uridine to uracil or the formation of alpha-D-ribose 1-phosphate. These assays are essential for validating CRISPR knockout or point-mutation models.
Metabolomics and flux analysis
Metabolomics can quantify uridine, uracil, and ribose-1-phosphate levels in cells with altered uridine phosphorylase activity. Isotope tracing with labeled uridine can reveal flux through salvage pathways and ribose recycling.
Transcriptomics and epigenomics
RNA-seq and DNA methylation analysis can identify changes in uridine phosphorylase expression and related pathway genes in disease models. These methods help link GO:0004850 to broader gene expression programs.
Proteomics and imaging
Proteomics can detect post-translational modifications and interaction partners of uridine phosphorylase, while fluorescence imaging of tagged knock-in models can reveal subcellular localization, including potential plasma membrane association.
How CRISPR Can Be Used to Study GO:0004850 uridine phosphorylase activity
Knockout
CRISPR knockout of UPP1 or UPP2 can abolish uridine phosphorylase activity, allowing researchers to study its role in pyrimidine salvage, ribose supply, and drug response. Knockout models are particularly useful for assessing metabolic vulnerabilities in cancer cells.
Point Mutation
Introducing point mutations in catalytic residues of UPP1 can separate enzyme activity from potential non-catalytic functions. Such models help confirm that observed phenotypes are due to loss of uridine phosphorylase activity.
Knock-in
Knock-in of tagged UPP1 (e.g., GFP or FLAG) enables visualization and immunoprecipitation of the enzyme, revealing its subcellular localization and interaction partners. This approach can also be used to introduce disease-associated variants.
Overexpression
Overexpression of UPP1 can increase uridine phosphorylase activity, leading to enhanced ribose-1-phosphate production and altered sensitivity to fluoropyrimidine drugs. Overexpression models are valuable for studying metabolic rewiring in cancer.
How EDITGENE Supports uridine phosphorylase activity Research
Researchers studying uridine phosphorylase activity-related genes often need to determine whether a candidate gene is causally involved in pyrimidine salvage, ribose recycling, or drug response. EDITGENE provides comprehensive CRISPR services to generate precisely engineered cell models that answer these questions.
Contact EDITGENE today to design your custom CRISPR model for uridine phosphorylase activity research.
Frequently Asked Questions About uridine phosphorylase activity
What is uridine phosphorylase activity?
Uridine phosphorylase activity (GO:0004850) is the catalysis of the reaction uridine + phosphate = uracil + alpha-D-ribose 1-phosphate, a key step in pyrimidine salvage.
What genes are involved in uridine phosphorylase activity?
The main genes are UPP1 and UPP2, which encode uridine phosphorylase enzymes, along with transporters and kinases that supply or use uridine.
What is the GO ID for uridine phosphorylase activity?
The Gene Ontology ID is GO:0004850, under the molecular_function aspect.
How is uridine phosphorylase activity regulated?
It is regulated by circadian rhythms in liver and by substrate availability through nucleoside transporters, as well as by metabolic stress in cancer.
Why is uridine phosphorylase activity important in cancer?
It supplies ribose-1-phosphate for glycolysis and nucleotide synthesis, supporting cancer cell growth under glucose limitation.
Can uridine phosphorylase activity be targeted for drug development?
Yes, inhibitors of uridine phosphorylase can modulate the efficacy of fluoropyrimidine prodrugs like 5'-deoxy-5-fluorouridine.
What diseases are linked to uridine phosphorylase activity?
It has been linked to pancreatic cancer, glioma, sepsis-induced acute lung injury, and mitochondrial metabolic disorders.
How do I measure uridine phosphorylase activity in the lab?
Common methods include HPLC-based enzyme assays and LC-MS metabolomics to quantify uridine, uracil, and ribose-1-phosphate.
What CRISPR models are available for studying uridine phosphorylase activity?
Knockout, point mutation, knock-in, and overexpression models can be generated for UPP1 and related genes.
Is uridine phosphorylase activity found outside the cytosol?
Yes, uridine phosphorylase activity has been detected in isolated plasma membranes of rat liver, suggesting compartmentalized functions.
Conclusion
Uridine phosphorylase activity (GO:0004850) is a central molecular function in pyrimidine salvage and ribose metabolism, with far-reaching implications for cancer, inflammation, and metabolic regulation. Its circadian control and role in drug activation make it a compelling target for both basic and translational research. By leveraging CRISPR knockout, point mutation, knock-in, and overexpression models, researchers can dissect the precise contributions of this activity to cellular physiology and disease. EDITGENE provides the tools and expertise to accelerate these discoveries.
References
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- 3. Sohn JH et al.. 2023. Liver mitochondrial cristae organizing protein MIC19 promotes energy expenditure and pedestrian locomotion by altering nucleotide metabolism.. Cell Metab 35(8):1356-1372.e5 PMID: 37473754
- 4. Bose R et al.. 1977. Uridine phosphorylase activity of isolated plasma membranes of rat liver.. Can J Biochem 55(5):528-33 PMID: 195683
- 5. Weng JY et al.. 2021. DNA Methylation Analysis Identifies Patterns in Progressive Glioma Grades to Predict Patient Survival.. Int J Mol Sci 22(3) PMID: 33498463
- 6. Skinner OS et al.. 2023. Salvage of ribose from uridine or RNA supports glycolysis in nutrient-limited conditions.. Nat Metab 5(5):765-776 PMID: 37198474
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- 8. Ishitsuka H et al.. 1980. Role of uridine phosphorylase for antitumor activity of 5'-deoxy-5-fluorouridine.. Gan 71(1):112-23 PMID: 6445847
