GO:0003937 IMP cyclohydrolase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0003937 IMP cyclohydrolase activity catalyzes the final step of de novo purine biosynthesis: IMP + H2O = 5-formamido-1-(5-phosphoribosyl)imidazole-4-carboxamide.
• In most organisms this activity is carried by the bifunctional enzyme ATIC (AICAR transformylase/IMP cyclohydrolase), which couples the last two steps of the pathway.
• ATIC and IMP cyclohydrolase activity are essential for de novo purine biosynthesis and for infection by pathogens such as Cryptococcus neoformans and Staphylococcus lugdunensis.
• The enzyme is a validated drug target: inhibitors of de novo purine synthesis promote AICAR accumulation and AMPK activation in muscle cells.
• ATIC is deregulated in cancer, including ALCL where NPM-ALK enhances its enzymatic activity, and atic loss impairs muscle homeostasis in zebrafish.
• CRISPR knockout, point-mutation, knock-in and overexpression models enable causal dissection of IMP cyclohydrolase function in disease and metabolism.
Description
IMP cyclohydrolase activity (GO:0003937) is a molecular function that catalyzes the reaction IMP + H2O = 5-formamido-1-(5-phosphoribosyl)imidazole-4-carboxamide, the terminal step in the de novo purine biosynthesis pathway. This reaction closes the purine ring to generate inosine monophosphate (IMP), the central branch-point metabolite from which AMP and GMP are derived. Because purines are required for DNA, RNA, ATP and GTP synthesis, the enzyme that carries this activity sits at a metabolic hub that influences proliferation, signaling and stress responses. In most organisms the activity is embedded in the bifunctional enzyme ATIC (AICAR transformylase/IMP cyclohydrolase), which catalyzes both the penultimate and final steps of the pathway. Researchers study GO:0003937 to understand nucleotide metabolism remodeling, to target pathogens that depend on de novo purine synthesis, and to interpret metabolic phenotypes in cancer and muscle biology. The activity is also experimentally tractable: archaeal and bacterial IMP cyclohydrolases have been purified and characterized, providing mechanistic and structural insights. This article integrates the QuickGO definition with verified PubMed literature to summarize the mechanism, key genes, disease links and CRISPR-based research strategies for GO:0003937.
IMP cyclohydrolase activity At A Glance
| GO ID | GO:0003937 |
|---|---|
| GO term | IMP cyclohydrolase activity |
| Ontology | molecular_function |
| Definition | Catalysis of the reaction: IMP + H2O = 5-formamido-1-(5-phosphoribosyl)imidazole-4-carboxamide |
| Synonym | IMP 1,2-hydrolase (decyclizing); IMP synthetase activity; inosinate cyclohydrolase activity; inosinicase activity |
| Major function | Terminal step of de novo purine biosynthesis, generating IMP |
| Representative enzyme | ATIC (bifunctional AICAR transformylase/IMP cyclohydrolase) |
| Pathway context | De novo purine biosynthesis; IMP is precursor to AMP and GMP |
| Organismal relevance | Essential for infection by Cryptococcus neoformans and studied in Staphylococcus lugdunensis and Candidatus Liberibacter asiaticus |
What Is GO:0003937?
IMP cyclohydrolase activity (GO:0003937) is defined by QuickGO as the catalysis of the reaction IMP + H2O = 5-formamido-1-(5-phosphoribosyl)imidazole-4-carboxamide. In other words, the enzyme hydrolyzes and cyclizes the formamido intermediate to form IMP, the first fully formed purine nucleotide of the de novo pathway. The reaction is reversible in principle but physiologically favors IMP formation during de novo purine biosynthesis. Synonyms include IMP 1,2-hydrolase (decyclizing), IMP synthetase activity, inosinate cyclohydrolase activity and inosinicase activity. In many organisms the activity is part of the bifunctional ATIC protein, which also carries AICAR transformylase activity.
Why Is IMP cyclohydrolase activity Important in Cell Biology?
IMP cyclohydrolase activity matters because it produces IMP, the metabolite that feeds all purine nucleotide synthesis and therefore controls cell proliferation, energy metabolism and signaling. Loss or inhibition of the activity blocks de novo purine biosynthesis, which is lethal or growth-restricting in pathogens and is exploited pharmacologically to elevate AICAR and activate AMPK. In humans, the bifunctional ATIC enzyme is linked to cancer biology, including ALCL where NPM-ALK enhances its activity, and to muscle homeostasis as shown by atic knockout zebrafish. Because the reaction is chemically well defined and genetically tractable, GO:0003937 is a productive entry point for CRISPR-based functional genomics, metabolic modeling and drug-target validation.
• Produces IMP, the central purine nucleotide precursor for AMP and GMP.
• Essential for de novo purine biosynthesis and infection in Cryptococcus neoformans.
• Required for normal growth and metabolism in Staphylococcus lugdunensis.
• Characterized in Candidatus Liberibacter asiaticus, informing pathogen-targeted strategies.
• Inhibition of de novo purine synthesis causes AICAR accumulation and AMPK activation.
• ATIC activity is enhanced by NPM-ALK in ALCL, linking the enzyme to lymphoma pathogenesis.
• atic knockout in zebrafish impairs skeletal muscle and oxidative phosphorylation.
• Nucleotide metabolism remodeling in macrophages involves this pathway.
• Archaeal IMP cyclohydrolases provide evolutionary and mechanistic models.
• Provides a defined enzymatic readout for CRISPR screens and metabolic assays.
Molecular Mechanism of IMP cyclohydrolase activity
Substrate binding and formamido intermediate
In simple terms: The enzyme grabs the formamido intermediate and prepares it to close into a ring.
IMP cyclohydrolase activity acts on 5-formamido-1-(5-phosphoribosyl)imidazole-4-carboxamide, the product of the preceding AICAR transformylase step, and converts it to IMP. In bifunctional ATIC enzymes, the IMP cyclohydrolase domain receives the formamido intermediate directly from the AICAR transformylase domain, channeling the substrate between active sites. Biochemical characterization of ATIC from Staphylococcus lugdunensis and Candidatus Liberibacter asiaticus confirms this substrate specificity and the bifunctional architecture.
Cyclization and hydrolysis to IMP
In simple terms: A water molecule helps the intermediate fold into the finished purine ring, making IMP.
The reaction catalyzed is IMP + H2O = 5-formamido-1-(5-phosphoribosyl)imidazole-4-carboxamide, meaning the enzyme promotes cyclization with concomitant hydrolysis to form the imidazole ring of IMP. This is the final step of de novo purine biosynthesis, after which IMP is aminated to AMP or oxidized to GMP. Archaeal IMP cyclohydrolases have been experimentally characterized, showing that the cyclohydrolase reaction is conserved across domains of life.
Bifunctional ATIC coupling
In simple terms: One protein contains two assembly-line stations, so the intermediate does not float away.
In many organisms, IMP cyclohydrolase activity resides in the C-terminal domain of ATIC, paired with AICAR transformylase activity in the N-terminal domain. This bifunctional arrangement couples the last two steps of de novo purine biosynthesis, improving pathway efficiency. Studies in Cryptococcus neoformans show that ATIC is essential for de novo purine biosynthesis and infection, confirming the physiological importance of the bifunctional enzyme.
Regulation by protein partners and post-translational inputs
In simple terms: Other proteins can turn the enzyme up or down without changing its amount.
The enzymatic activity of ATIC can be enhanced by oncogenic fusion proteins; NPM-ALK increases AICAR transformylase/IMP cyclohydrolase activity, providing a direct link between a kinase-driven malignancy and purine biosynthesis. Nucleotide metabolism remodeling in classically activated macrophages is driven by nitric oxide, indicating that the pathway containing this activity is subject to inflammatory regulation. These observations position IMP cyclohydrolase activity within signaling networks rather than as an isolated housekeeping reaction.
Inhibition and metabolic consequences
In simple terms: Blocking the pathway makes upstream molecules pile up and triggers energy sensors.
Diverse inhibitors of de novo purine synthesis promote AICAR-induced AMPK activation and glucose uptake in L6 myotubes, demonstrating that interrupting the pathway that includes IMP cyclohydrolase activity has measurable metabolic consequences. Because AICAR accumulates when the pathway is blocked, the activity serves as a node for pharmacological and genetic interrogation. In zebrafish, atic knockout causes skeletal muscle atrophy that is ameliorated by aerobic exercise through the oxidative phosphorylation pathway, linking the enzyme to muscle energy metabolism.
Key Genes Involved in GO:0003937 IMP cyclohydrolase activity
The genes and proteins below are directly implicated in IMP cyclohydrolase activity (GO:0003937) or in the de novo purine biosynthesis pathway that contains it, based on the verified literature.
| Gene | Major Role | Research Relevance |
|---|---|---|
| ATIC | Bifunctional AICAR transformylase/IMP cyclohydrolase; carries GO:0003937 | Core enzyme for de novo purine biosynthesis; studied in pathogens and human disease |
| ATIC (S. lugdunensis) | Bacterial ATIC with AICAR transformylase and IMP cyclohydrolase activities | Antibacterial target characterization |
| ATIC (C. Liberibacter asiaticus) | Bifunctional ATIC in a plant pathogen | Pathogen metabolism and inhibitor design |
| ATIC (C. neoformans) | Essential for de novo purine biosynthesis and infection | Fungal virulence model |
| atic (zebrafish) | Required for skeletal muscle homeostasis | Knockout model for muscle atrophy and oxidative phosphorylation |
| NPM-ALK | Oncogenic fusion that enhances ATIC enzymatic activity | ALCL pathogenesis and targeted therapy |
| AMPK | Energy sensor activated by AICAR accumulation when purine synthesis is inhibited | Metabolic regulation and glucose uptake |
| Nitric oxide pathway | Drives nucleotide metabolism remodeling in macrophages | Inflammation and immunometabolism |
| Archaeal IMP cyclohydrolases | Experimentally characterized cyclohydrolases | Evolutionary and mechanistic studies |
| AICAR transformylase domain | Penultimate pathway step coupled to IMP cyclohydrolase | Bifunctional enzyme architecture |
| IMP cyclohydrolase domain | Catalytic domain for GO:0003937 | Structure-function and inhibitor studies |
| De novo purine pathway enzymes | Provide substrate for IMP cyclohydrolase | Pathway flux and metabolic modeling |
| Purine salvage enzymes | Alternative route to IMP | Comparative metabolism and redundancy |
| ATIC in ALCL cells | Activity enhanced by NPM-ALK | Lymphoma experimental models |
| ATIC in L6 myotubes | Pathway inhibited by purine synthesis inhibitors | Muscle glucose uptake studies |
| ATIC in macrophages | Nucleotide metabolism remodeling | Immunometabolism research |
How Is IMP cyclohydrolase activity Regulated?
IMP cyclohydrolase activity is regulated at multiple levels. Genetically, expression of the bifunctional ATIC enzyme determines pathway capacity, and loss of ATIC abolishes de novo purine biosynthesis and infection in Cryptococcus neoformans. Post-translationally, the enzymatic activity of ATIC can be enhanced by the NPM-ALK oncogenic fusion, linking kinase signaling to purine biosynthesis in ALCL. Metabolically, the pathway is responsive to inflammatory cues: classically activated macrophages undergo nucleotide metabolism remodeling driven by nitric oxide. Pharmacologically, inhibition of de novo purine synthesis causes AICAR accumulation and AMPK activation, showing that the pathway is coupled to energy sensing. In muscle, atic knockout alters oxidative phosphorylation, indicating that the activity influences mitochondrial and energetic programs.
IMP cyclohydrolase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| ATIC | ALCL / lymphoma pathogenesis via NPM-ALK | ATIC knockout or point-mutation lymphoma cell lines |
| atic | Skeletal muscle atrophy and oxidative phosphorylation defects | Zebrafish atic knockout with exercise intervention |
| ATIC | Fungal infection by Cryptococcus neoformans | Cryptococcus atic deletion strains |
| ATIC | Bacterial infection and pathogen metabolism | Staphylococcus lugdunensis and Candidatus Liberibacter asiaticus ATIC assays |
| ATIC pathway | AMPK activation and glucose uptake in muscle | L6 myotubes treated with purine synthesis inhibitors |
Cancer and ALCL
ATIC enzymatic activity, including IMP cyclohydrolase activity, is enhanced by NPM-ALK, providing new insights into ALK-mediated pathogenesis and the treatment of anaplastic large cell lymphoma (ALCL). This link suggests that purine biosynthesis supports the metabolic demands of ALK-driven lymphoma and that the pathway may be therapeutically actionable.
Metabolic and muscle disorders
Aerobic exercise ameliorates skeletal muscle atrophy in atic knockout zebrafish through the oxidative phosphorylation pathway, indicating that loss of ATIC function perturbs muscle energy metabolism. Inhibitors of de novo purine synthesis promote AICAR-induced AMPK activation and glucose uptake in L6 myotubes, connecting the pathway to glucose homeostasis and insulin sensitivity.
Infectious disease
ATIC is essential for de novo purine biosynthesis and infection by Cryptococcus neoformans, making the fungal enzyme a potential antifungal target. The bifunctional ATIC from Staphylococcus lugdunensis and Candidatus Liberibacter asiaticus has been biochemically characterized, supporting pathogen-directed inhibitor discovery.
Inflammation and immunometabolism
Classically activated macrophages undergo functionally significant nucleotide metabolism remodeling driven by nitric oxide, implicating the de novo purine pathway that contains IMP cyclohydrolase activity in inflammatory macrophage function.
From IMP cyclohydrolase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Is ATIC required for de novo purine biosynthesis and infection? | Knockout in Cryptococcus neoformans |
| How does loss of atic affect muscle homeostasis? | Zebrafish atic knockout |
| Does a catalytic residue mutation abolish IMP cyclohydrolase activity? | Point-mutation knock-in of ATIC catalytic residues |
| Can tagged ATIC be used to monitor localization and interactions? | Tagged knock-in of ATIC |
| Does ATIC overexpression enhance purine flux and proliferation? | Overexpression of ATIC in cell lines |
| Which genes buffer loss of IMP cyclohydrolase activity? | CRISPR library screening in ATIC-knockout background |
How to Study the IMP cyclohydrolase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| IMP cyclohydrolase enzymatic assay | Conversion of formamido intermediate to IMP | Validate ATIC mutants and inhibitors |
| Metabolomics | Purine nucleotide levels including IMP and AICAR | Pathway flux and drug response |
| CRISPR knockout | Loss-of-function phenotype | Essentiality in pathogens and muscle cells |
| Site-directed mutagenesis | Catalytic residue requirement | Mechanistic dissection of GO:0003937 |
| Co-immunoprecipitation | Protein-protein interactions | NPM-ALK and ATIC regulation |
| AMPK activation assay | Phosphorylation of AMPK | Metabolic consequence of pathway inhibition |
| Zebrafish exercise model | Muscle atrophy and oxidative phosphorylation | In vivo function of atic |
| Fungal infection model | Virulence and purine auxotrophy | ATIC essentiality in Cryptococcus |
Enzymatic assays for IMP cyclohydrolase activity
Direct measurement of IMP cyclohydrolase activity uses the conversion of the formamido intermediate to IMP, as performed for ATIC from Staphylococcus lugdunensis, Candidatus Liberibacter asiaticus and archaeal enzymes. These assays provide the definitive functional readout for GO:0003937 and are used to validate mutants and inhibitors.
Metabolomics and nucleotide profiling
Because the reaction produces IMP, metabolomic profiling of purine nucleotides can report pathway flux and the consequences of genetic or pharmacological perturbation. AICAR accumulation is a sensitive marker of pathway inhibition and is linked to AMPK activation.
Genetic and CRISPR perturbation
Knockout of ATIC in Cryptococcus neoformans and atic knockout in zebrafish demonstrate how genetic loss-of-function reveals the physiological roles of the activity. These models can be combined with rescue experiments to confirm causality.
Protein interaction and signaling studies
Co-immunoprecipitation and activity assays showed that NPM-ALK enhances ATIC enzymatic activity, illustrating how signaling proteins modulate the function. Such approaches connect GO:0003937 to oncogenic networks.
How CRISPR Can Be Used to Study GO:0003937 IMP cyclohydrolase activity
Knockout
CRISPR knockout of ATIC or its homologs is used to test whether IMP cyclohydrolase activity is essential for de novo purine biosynthesis, infection and muscle homeostasis. In Cryptococcus neoformans, ATIC deletion impairs infection, and in zebrafish atic knockout causes muscle atrophy, demonstrating the power of knockout models.
Point Mutation
Point mutations in catalytic residues of the IMP cyclohydrolase domain can separate the cyclohydrolase activity from the AICAR transformylase activity of bifunctional ATIC. Such mutants are valuable for assigning specific phenotypes to GO:0003937 rather than to the upstream step.
Knock-in
Knock-in of epitope-tagged ATIC allows localization, interaction and activity measurements in native chromatin context, complementing biochemical studies of the enzyme. Tagged knock-in can also be used to rescue knockout phenotypes and confirm that the tagged protein retains IMP cyclohydrolase activity.
Overexpression
Overexpression of ATIC can enhance purine biosynthesis and has been linked to increased enzymatic activity in the context of NPM-ALK in ALCL. Overexpression models help determine whether increased IMP cyclohydrolase activity is sufficient to drive proliferation or metabolic reprogramming.
How EDITGENE Supports IMP cyclohydrolase activity Research
Researchers studying IMP cyclohydrolase activity-related genes often need to determine whether a candidate gene is causally involved in purine metabolism, infection or disease phenotypes. EDITGENE provides CRISPR-based cell models and screening services that make these causal experiments routine, from knockout validation to precise point mutations and tagged knock-ins.
Contact EDITGENE today to design your custom CRISPR model for IMP cyclohydrolase activity research.
Frequently Asked Questions About IMP cyclohydrolase activity
What is IMP cyclohydrolase activity?
IMP cyclohydrolase activity (GO:0003937) is the molecular function that catalyzes IMP + H2O = 5-formamido-1-(5-phosphoribosyl)imidazole-4-carboxamide, the final step of de novo purine biosynthesis.
What genes are involved in IMP cyclohydrolase activity?
The main gene is ATIC, which encodes a bifunctional AICAR transformylase/IMP cyclohydrolase; homologs exist in bacteria, fungi and archaea.
Which enzyme carries GO:0003937?
In most organisms the activity is carried by ATIC, a bifunctional enzyme that also performs the upstream AICAR transformylase step.
What reaction does IMP cyclohydrolase catalyze?
It catalyzes the cyclization and hydrolysis of 5-formamido-1-(5-phosphoribosyl)imidazole-4-carboxamide to form IMP.
Why is IMP cyclohydrolase activity important for pathogens?
ATIC is essential for de novo purine biosynthesis and infection by Cryptococcus neoformans, and has been characterized in Staphylococcus lugdunensis and Candidatus Liberibacter asiaticus.
How is IMP cyclohydrolase activity linked to cancer?
NPM-ALK enhances ATIC enzymatic activity in ALCL, linking purine biosynthesis to ALK-mediated lymphoma pathogenesis.
Can IMP cyclohydrolase activity be inhibited pharmacologically?
Yes, inhibitors of de novo purine synthesis promote AICAR accumulation and AMPK activation in muscle cells.
What happens when atic is knocked out?
In zebrafish, atic knockout causes skeletal muscle atrophy that is ameliorated by aerobic exercise via oxidative phosphorylation.
How do you measure IMP cyclohydrolase activity?
Direct enzymatic assays monitor conversion of the formamido intermediate to IMP, as done for bacterial and archaeal enzymes.
What CRISPR models are used to study GO:0003937?
Knockout, point-mutation, knock-in and overexpression models in cell lines and organisms are used to dissect the function of ATIC and the purine pathway.
Conclusion
IMP cyclohydrolase activity (GO:0003937) is the terminal catalytic step of de novo purine biosynthesis, producing IMP and feeding all downstream purine nucleotide synthesis. Its bifunctional carrier ATIC is essential in pathogens, is deregulated in cancer and influences muscle energy metabolism, making the activity a compelling target for mechanistic and therapeutic research. CRISPR-based knockout, point-mutation, knock-in and overexpression models provide the causal toolkit needed to move from correlation to function in this pathway.
References
- 1. John SV et al.. 2025. Classically activated macrophages undergo functionally significant nucleotide metabolism remodelling driven by nitric oxide.. Nat Metab 7(8):1681-1702 PMID: 40759751
- 2. Lonare S et al.. 2024. Characterization of AICAR transformylase/IMP cyclohydrolase (ATIC) bifunctional enzyme from Candidatus Liberibacer asiaticus.. Biochim Biophys Acta Proteins Proteom 1872(4):141015 PMID: 38615986
- 3. Verma P et al.. 2017. Characterization of AICAR transformylase/IMP cyclohydrolase (ATIC) from Staphylococcus lugdunensis.. FEBS J 284(24):4233-4261 PMID: 29063699
- 4. Peng Z et al.. 2025. Aerobic exercise ameliorates skeletal muscle atrophy in atic knockout zebrafish through the oxidative phosphorylation pathway.. Free Radic Biol Med 238:653-668 PMID: 40623538
- 5. Boccalatte FE et al.. 2009. The enzymatic activity of 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/IMP cyclohydrolase is enhanced by NPM-ALK: new insights in ALK-mediated pathogenesis and the treatment of ALCL.. Blood 113(12):2776-90 PMID: 18845790
- 6. Dolinar K et al.. 2025. Diverse Inhibitors of De Novo Purine Synthesis Promote AICAR-Induced AMPK Activation and Glucose Uptake in L6 Myotubes.. Biofactors 51(4):e70037 PMID: 40793247
- 7. Wizrah MSI et al.. 2022. AICAR transformylase/IMP cyclohydrolase (ATIC) is essential for de novo purine biosynthesis and infection by Cryptococcus neoformans.. J Biol Chem 298(10):102453 PMID: 36063996
- 8. Hunter CA et al.. 2019. Experimental characterization of two archaeal inosine 5'-monophosphate cyclohydrolases.. PLoS One 14(10):e0223983 PMID: 31622427
