GO:0003922 GMP synthase (glutamine-hydrolyzing) activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0003922 describes the enzymatic activity that converts xanthosine 5'-monophosphate (XMP) to guanosine 5'-monophosphate (GMP) using ATP and L-glutamine.
• The reaction is a two-step process: glutamine hydrolysis releases ammonia, which is then used to aminate XMP to GMP, consuming ATP.
• The human enzyme, GMPS, is a bifunctional protein with a glutamine amidotransferase domain and an ATP pyrophosphatase domain.
• GMPS is essential for guanine nucleotide biosynthesis and is a validated target in cancer and fungal infections.
• Structural studies reveal allosteric regulation and a conserved catalytic cysteine essential for glutamine hydrolysis.
• CRISPR-based models (knockout, point mutation, knock-in) enable precise dissection of GMPS function in disease and development.
Description
GMP synthase (glutamine-hydrolyzing) activity, encoded by the GO term GO:0003922, is a fundamental enzymatic activity in purine metabolism. It catalyzes the final step of guanine nucleotide biosynthesis, converting xanthosine 5'-monophosphate (XMP) to guanosine 5'-monophosphate (GMP) through a glutamine-dependent amidation reaction that also consumes ATP. This activity is essential for maintaining cellular guanine nucleotide pools, which are required for DNA and RNA synthesis, protein glycosylation, and signal transduction. In humans, the enzyme is known as GMPS (guanosine monophosphate synthetase), and its dysfunction or overexpression has been linked to cancer progression and metabolic reprogramming. In pathogens such as Cryptococcus neoformans and Aspergillus fumigatus, GMP synthase is critical for virulence and survival, making it an attractive antifungal target. Understanding the molecular mechanism, regulation, and disease relevance of GO:0003922 is therefore of broad biomedical importance.
GMP synthase (glutamine-hydrolyzing) activity At A Glance
| GO ID | GO:0003922 |
|---|---|
| GO term | GMP synthase (glutamine-hydrolyzing) activity |
| Ontology | molecular_function |
| Synonym | glutamine amidotransferase activity; GMP synthetase (glutamine-hydrolyzing); xanthosine 5'-phosphate amidotransferase activity |
| Major function | Catalyzes the conversion of XMP to GMP using glutamine as nitrogen donor and ATP as energy source |
| Reaction | ATP + XMP + L-glutamine + H2O = AMP + diphosphate + GMP + L-glutamate + 2H+ |
| EC number | 6.3.5.2 |
| Pathway | Purine metabolism; guanine nucleotide biosynthesis |
What Is GO:0003922?
GO:0003922, GMP synthase (glutamine-hydrolyzing) activity, is defined as the catalysis of the reaction: ATP + XMP + L-glutamine + H2O = AMP + diphosphate + GMP + L-glutamate + 2H+. In other words, it is the enzyme activity that uses the amide group of glutamine to convert XMP into GMP, with the concomitant hydrolysis of ATP to AMP and diphosphate. This activity is synonymous with glutamine amidotransferase activity, GMP synthetase, and xanthosine 5'-phosphate amidotransferase activity, reflecting its dual role in ammonia transfer and nucleotide synthesis.
Why Is GMP synthase (glutamine-hydrolyzing) activity Important in Cell Biology?
GO:0003922 is critical because it represents the terminal step in guanine nucleotide biosynthesis, a process that is essential for cell proliferation, DNA replication, and RNA synthesis. Dysregulation of GMP synthase activity has been implicated in cancer, where increased guanine nucleotide synthesis supports tumor growth. In pathogens, the enzyme is required for virulence factor production and infection, highlighting its potential as an antimicrobial target. Moreover, the unique two-domain architecture and allosteric regulation of GMP synthetases make them a paradigm for understanding glutamine amidotransferases and metabolic channeling.
• Essential for de novo guanine nucleotide biosynthesis, supplying GMP for RNA and DNA.
• Validated therapeutic target in lung adenocarcinoma, where GMPS expression is elevated.
• Required for virulence in Cryptococcus neoformans, a fungal pathogen.
• Structural and mechanistic insights inform antifungal drug design against Aspergillus fumigatus.
• Model enzyme for studying glutamine amidotransferase mechanisms and allostery.
• Inhibition of GMP synthesis by mycophenolate mofetil impacts immune cell proliferation.
• Mutations in the catalytic cysteine abolish glutamine hydrolysis, linking activity to specific residues.
• Provides a metabolic checkpoint linking nucleotide availability to cell cycle progression.
• Potential biomarker for metabolic reprogramming in cancer.
• Enables CRISPR-based functional genomics to dissect nucleotide metabolism in disease models.
Molecular Mechanism of GMP synthase (glutamine-hydrolyzing) activity
Substrate Binding and Domain Architecture
In simple terms: The enzyme has two main parts: one grabs glutamine, the other grabs XMP and ATP.
GMP synthase is a bifunctional enzyme composed of a glutamine amidotransferase (GATase) domain and an ATP pyrophosphatase (ATPPase) domain. The GATase domain binds L-glutamine and catalyzes its hydrolysis to glutamate and ammonia, while the ATPPase domain binds XMP and ATP, activating XMP for amination. Structural studies of human GMPS and fungal orthologs reveal a tetrameric organization with allosteric communication between subunits.
Glutamine Hydrolysis and Ammonia Transfer
In simple terms: Glutamine is split to release ammonia, which is then used to convert XMP to GMP.
The glutamine hydrolysis step occurs in the GATase domain and requires an essential active-site cysteine residue, as demonstrated by mutagenesis of human GMP synthetase. The released ammonia is channeled through a molecular tunnel to the ATPPase active site, where it attacks the activated XMP intermediate. This channeling prevents ammonia loss and ensures efficient amidation.
ATP-Dependent Activation of XMP
In simple terms: ATP provides energy to make XMP reactive so it can accept the ammonia.
In the ATPPase domain, ATP reacts with XMP to form a high-energy intermediate, adenylyl-XMP, releasing pyrophosphate. This intermediate then reacts with ammonia to form GMP and AMP. The reaction is thus ATP-dependent and produces AMP and diphosphate as byproducts.
Allosteric Regulation and Conformational Changes
In simple terms: The enzyme can change shape to control its activity, responding to cellular signals.
GMP synthetases exhibit allosteric regulation, with structural studies showing that binding of substrates or analogs induces conformational changes that modulate catalysis. For example, the human enzyme is inhibited by GMP, providing feedback control. In fungal pathogens, unique structural features may offer opportunities for selective inhibition.
Catalytic Cycle and Product Release
In simple terms: After GMP is made, it is released and the enzyme resets for another round.
The catalytic cycle involves ordered substrate binding and product release, with GMP and AMP dissociating from the enzyme. The overall reaction consumes one ATP and one glutamine per GMP formed, linking guanine nucleotide synthesis to cellular energy status.
Key Genes Involved in GO:0003922 GMP synthase (glutamine-hydrolyzing) activity
The following genes and proteins are directly involved in or regulate GMP synthase (glutamine-hydrolyzing) activity and its associated pathways.
| Gene | Major Role | Research Relevance |
|---|---|---|
| GMPS | Encodes human GMP synthase; catalyzes XMP to GMP conversion | Cancer target; essential for guanine nucleotide synthesis |
| GATase domain | Glutamine hydrolysis and ammonia production | Mechanistic studies; essential cysteine identified |
| ATPPase domain | ATP-dependent activation of XMP | Structural and kinetic studies |
| Cys104 (human GMPS) | Essential active-site cysteine for glutamine hydrolysis | Mutagenesis confirms catalytic role |
| GUA1 (yeast) | Ortholog of GMPS in Saccharomyces cerevisiae | Model for genetic studies |
| GuaA (Aspergillus fumigatus) | Fungal GMP synthase | Antifungal target; structural insights |
| GUA1 (Cryptococcus neoformans) | Required for virulence factor production | Infection model |
| IMPDH | Inosine monophosphate dehydrogenase; upstream of GMPS | Target of mycophenolate mofetil |
| PRPP synthetase | Provides PRPP for purine synthesis | Linked to nucleotide metabolism |
| GMP reductase | Converts GMP to IMP | Regulates guanine nucleotide pools |
| NUDT5 | Hydrolase involved in nucleotide metabolism | Potential regulator |
| ATIC | Bifunctional purine biosynthesis enzyme | Parallel pathway |
| GART | Phosphoribosylglycinamide formyltransferase | Purine synthesis |
| PAICS | Multifunctional purine biosynthesis enzyme | Purine synthesis |
| ADSL | Adenylosuccinate lyase | Purine synthesis |
| GUK1 | Guanylate kinase | Phosphorylates GMP to GDP |
| NDK | Nucleoside diphosphate kinase | Maintains nucleotide pools |
| RRM1 | Ribonucleotide reductase subunit | Provides deoxyribonucleotides |
How Is GMP synthase (glutamine-hydrolyzing) activity Regulated?
GMP synthase activity is regulated at multiple levels. Allosteric feedback inhibition by GMP controls flux through the pathway. In cancer cells, GMPS expression can be upregulated in response to increased demand for guanine nucleotides, as observed in lung adenocarcinoma. The enzyme may also be subject to post-translational modifications, though specific regulators remain to be fully defined. In pathogens, GMP synthase is essential for virulence and its expression is likely tied to metabolic adaptation during infection.
GMP synthase (glutamine-hydrolyzing) activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| GMPS | Lung adenocarcinoma | CRISPR knockout in A549 or H1299 cells |
| GUA1 | Cryptococcosis | Knockout in Cryptococcus neoformans |
| GuaA | Aspergillosis | Point mutations in Aspergillus fumigatus |
| GMPS | Metabolic disorders | Knock-in of patient variants in cell lines |
| IMPDH | Immunosuppression | Overexpression in T cells |
Cancer
GMPS is overexpressed in lung adenocarcinoma and supports tumor growth by sustaining guanine nucleotide pools. Targeting GMPS with inhibitors or genetic knockout reduces proliferation, suggesting it as a therapeutic target. The enzyme's role in nucleotide synthesis links it to metabolic reprogramming in cancer.
Fungal Infections
In Cryptococcus neoformans, GMP synthase is required for virulence factor production and infection, making it a potential antifungal target. Structural studies of Aspergillus fumigatus GMP synthase provide a basis for designing selective inhibitors.
Immune Disorders
Mycophenolate mofetil, an inhibitor of IMPDH (upstream of GMPS), is used as an immunosuppressant, highlighting the importance of guanine nucleotide synthesis in immune cell proliferation. Direct inhibition of GMPS could have similar immunomodulatory effects.
From GMP synthase (glutamine-hydrolyzing) activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does GMPS loss affect cancer cell proliferation? | CRISPR knockout in lung adenocarcinoma cell lines |
| What is the role of the catalytic cysteine? | Point mutation (C104S) in human GMPS |
| How does GMPS contribute to fungal virulence? | Knockout in Cryptococcus neoformans |
| Can GMPS be targeted by small molecules? | Structural studies and inhibitor testing in Aspergillus fumigatus |
| Does GMPS overexpression drive nucleotide pool expansion? | Overexpression in mammalian cells |
| How is GMPS regulated by feedback inhibition? | Knock-in of allosteric mutants |
How to Study the GMP synthase (glutamine-hydrolyzing) activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Enzymatic assay | GMP synthase activity | Kinetic studies |
| X-ray crystallography | Three-dimensional structure | Mechanistic insights |
| CRISPR knockout | Gene essentiality | Cancer target validation |
| Metabolomics | Nucleotide levels | Pathway flux |
| Site-directed mutagenesis | Residue function | Catalytic cysteine |
| Antifungal susceptibility testing | Pathogen growth | Drug target validation |
| RNA-seq | Gene expression changes | Pathway regulation |
Enzymatic Assays
GMP synthase activity can be measured spectrophotometrically by coupling the production of GMP or AMP to NADH oxidation. Radioactive assays using [14C]XMP or [14C]glutamine are also used.
Structural Biology
X-ray crystallography and cryo-EM have revealed the architecture of GMP synthetases from human and fungal sources, providing insights into catalysis and allostery.
CRISPR Screening
Genome-wide CRISPR knockout screens can identify GMPS as essential in cancer cell lines, linking it to proliferation and survival.
Metabolomics
LC-MS-based metabolomics quantifies guanine nucleotide pools and flux through the pathway, revealing changes upon GMPS perturbation.
How CRISPR Can Be Used to Study GO:0003922 GMP synthase (glutamine-hydrolyzing) activity
Knockout
CRISPR knockout of GMPS in cancer cell lines reduces guanine nucleotide levels and inhibits proliferation, validating it as a therapeutic target. In Cryptococcus neoformans, knockout of GUA1 attenuates virulence.
Point Mutation
Point mutations such as C104S in human GMPS abolish glutamine hydrolysis, allowing dissection of the catalytic mechanism. Such mutants can be introduced via CRISPR prime editing or homology-directed repair.
Knock-in
Knock-in of tagged GMPS (e.g., GFP or FLAG) enables localization and interaction studies. Knock-in of patient-derived variants can model disease-associated mutations.
Overexpression
CRISPR activation (CRISPRa) or lentiviral overexpression of GMPS can model increased nucleotide synthesis in cancer. Overexpression in fungal pathogens can test gain-of-function phenotypes.
How EDITGENE Supports GMP synthase (glutamine-hydrolyzing) activity Research
Researchers studying GMP synthase (glutamine-hydrolyzing) activity-related genes often need to determine whether a candidate gene is causally involved in nucleotide metabolism, cancer proliferation, or pathogen virulence. EDITGENE provides comprehensive CRISPR-based services to generate precisely engineered cell models for such investigations.
Contact EDITGENE today to design your custom CRISPR model for GMP synthase (glutamine-hydrolyzing) activity research.
Frequently Asked Questions About GMP synthase (glutamine-hydrolyzing) activity
What is GMP synthase (glutamine-hydrolyzing) activity?
It is the enzymatic activity (GO:0003922) that converts XMP to GMP using glutamine and ATP, essential for guanine nucleotide synthesis.
What genes are involved in GMP synthase (glutamine-hydrolyzing) activity?
The primary gene is GMPS in humans, with orthologs such as GUA1 in yeast and fungi.
What is the reaction catalyzed by GMP synthase?
ATP + XMP + L-glutamine + H2O = AMP + diphosphate + GMP + L-glutamate + 2H+.
Why is GMP synthase important in cancer?
GMPS is overexpressed in lung adenocarcinoma and supports tumor proliferation by maintaining guanine nucleotide pools.
Is GMP synthase a drug target?
Yes, it is a validated target in cancer and fungal infections, with structural studies guiding inhibitor design.
What is the role of the cysteine residue in GMP synthase?
Cysteine 104 in human GMPS is essential for glutamine hydrolysis; mutation abolishes activity.
How is GMP synthase regulated?
It is feedback-inhibited by GMP and may be regulated by cellular demand for nucleotides.
What diseases are associated with GMP synthase dysfunction?
Cancer, fungal infections, and immune disorders linked to nucleotide metabolism.
How can CRISPR be used to study GMP synthase?
CRISPR knockout, point mutation, knock-in, and overexpression models enable functional dissection.
What methods measure GMP synthase activity?
Enzymatic assays, metabolomics, and structural biology are commonly used.
Conclusion
GMP synthase (glutamine-hydrolyzing) activity (GO:0003922) is a central enzymatic activity in guanine nucleotide biosynthesis with broad implications for cancer, infectious disease, and immunology. Its unique two-domain architecture and allosteric regulation make it a fascinating subject for mechanistic studies. CRISPR-based models are invaluable for dissecting its roles in health and disease, and EDITGENE offers tailored services to support such research.
References
- 1. Ballut L et al.. 2023. GMP Synthetase: Allostery, Structure, and Function.. Biomolecules 13(9) PMID: 37759779
- 3. Yu M et al.. 2025. Circulating metabolomics reveals guanosine monophosphate synthetase (GMPS) as a novel therapeutic target in lung adenocarcinoma.. J Pathol 266(4-5):465-480 PMID: 40539844
- 4. Ballut L et al.. 2022. Tertiary and Quaternary Structure Organization in GMP Synthetases: Implications for Catalysis.. Biomolecules 12(7) PMID: 35883427
- 5. Chitty JL et al.. 2017. GMP Synthase Is Required for Virulence Factor Production and Infection by Cryptococcus neoformans.. J Biol Chem 292(7):3049-3059 PMID: 28062578
- 6. Nakamura J et al.. 1995. The glutamine hydrolysis function of human GMP synthetase. Identification of an essential active site cysteine.. J Biol Chem 270(40):23450-5 PMID: 7559506
- 7. Ishikawa H. 1999. Mizoribine and mycophenolate mofetil.. Curr Med Chem 6(7):575-97 PMID: 10390602
- 8. Nguyen S et al.. 2022. Structural insights into the antifungal drug target guanosine monophosphate synthase from Aspergillus fumigatus.. Acta Crystallogr D Struct Biol 78(Pt 2):248-259 PMID: 35102890
