GO:0004477 methenyltetrahydrofolate cyclohydrolase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0004477 describes the enzymatic hydrolysis of 5,10-methenyltetrahydrofolate to 10-formyltetrahydrofolate, a central reaction in one-carbon metabolism.
• In eukaryotes, this activity is typically carried by bifunctional or trifunctional enzymes such as MTHFD1, MTHFD2, and MTHFD2L, which also possess dehydrogenase and synthetase activities.
• The cyclohydrolase step is often rate-limiting for the conversion of 10-formyltetrahydrofolate to 5,10-methylenetetrahydrofolate in bifunctional enzymes.
• Structural and biochemical studies have revealed that the cyclohydrolase domain can be allosterically stimulated by NADP+ binding to the dehydrogenase domain.
• Dysregulation of MTHFD2, which harbors this activity, is implicated in cancer and is under investigation as a therapeutic target.
• Studying GO:0004477 requires integrating enzymology, structural biology, and CRISPR-based models to dissect its role in folate metabolism and disease.
Description
Methenyltetrahydrofolate cyclohydrolase activity (GO:0004477) is a molecular function that catalyzes the reversible hydrolysis of 5,10-methenyltetrahydrofolate to 10-formyltetrahydrofolate. This reaction is a key step in one-carbon metabolism, interconverting folate derivatives that are essential for purine and thymidylate biosynthesis, as well as for methionine regeneration. In mammals, the activity is typically found as part of larger multifunctional enzymes, such as MTHFD1, MTHFD2, and MTHFD2L, which combine dehydrogenase, cyclohydrolase, and sometimes synthetase activities. Understanding GO:0004477 is therefore critical for researchers studying nucleotide metabolism, mitochondrial one-carbon flux, and cancer cell proliferation. The cyclohydrolase reaction is often rate-limiting within bifunctional dehydrogenase-cyclohydrolase enzymes, making it a key regulatory node. Moreover, structural studies have provided insights into the catalytic mechanism and allosteric regulation of this activity. This article synthesizes current knowledge on GO:0004477, its genetic players, and experimental approaches to study it.
methenyltetrahydrofolate cyclohydrolase activity At A Glance
| GO ID | GO:0004477 |
|---|---|
| GO term | methenyltetrahydrofolate cyclohydrolase activity |
| Ontology | molecular_function |
| Synonym | 5,10-methenyltetrahydrofolate 5-hydrolase (decyclizing) |
| Synonym | 5,10-methenyl-THF cyclohydrolase activity |
| Synonym | citrovorum factor cyclodehydrase activity |
| Synonym | formyl-methenyl-methylenetetrahydrofolate synthetase (combined) |
| Major function | Interconverts 5,10-methenyltetrahydrofolate and 10-formyltetrahydrofolate in one-carbon metabolism. |
| EC number | 3.5.4.9 |
| Reaction | 5,10-methenyltetrahydrofolate + H2O = 10-formyltetrahydrofolate |
| Cofactor | NADP+ (for some bifunctional enzymes) |
What Is GO:0004477?
GO:0004477, methenyltetrahydrofolate cyclohydrolase activity, is defined as the catalysis of the reaction: 5,10-methenyltetrahydrofolate + H2O = 10-formyltetrahydrofolate. This enzymatic activity hydrolyzes the imidazolinium ring of 5,10-methenyltetrahydrofolate, opening it to yield 10-formyltetrahydrofolate. It is a reversible reaction that plays a central role in folate-mediated one-carbon transfer.
Why Is methenyltetrahydrofolate cyclohydrolase activity Important in Cell Biology?
GO:0004477 is essential for maintaining the balance of one-carbon folate pools that feed into purine synthesis, thymidylate synthesis, and methionine cycle. Its dysregulation has been linked to cancer, where MTHFD2 is often overexpressed to support rapid proliferation. The cyclohydrolase step is rate-limiting in bifunctional enzymes, making it a key control point. Therefore, understanding this activity is crucial for both basic metabolism research and therapeutic development.
• Provides 10-formyltetrahydrofolate for de novo purine synthesis.
• Supports thymidylate synthesis by interconverting folate species.
• Rate-limiting step in bifunctional dehydrogenase-cyclohydrolase enzymes.
• MTHFD2, containing this activity, is a cancer drug target.
• Allosteric regulation by NADP+ links redox state to cyclohydrolase function.
• Mitochondrial isoforms (MTHFD2, MTHFD2L) are critical for embryonic development.
• Involved in formate production for cytoplasmic one-carbon pools.
• Potential role in non-enzymatic regulation by NUDT5 in purine synthesis.
• Structural insights aid inhibitor design.
• Relevance to antifolate chemotherapy and drug resistance.
What Happens During methenyltetrahydrofolate cyclohydrolase activity?
Substrate Binding and Ring Opening
In simple terms: The enzyme grabs a folate molecule and opens its ring using water.
The cyclohydrolase domain binds 5,10-methenyltetrahydrofolate and catalyzes the hydrolytic opening of the imidazolinium ring, yielding 10-formyltetrahydrofolate. This step is reversible and requires a water molecule.
Rate-Limiting Nature in Bifunctional Enzymes
In simple terms: This step is often the slowest in a multi-step enzyme assembly line.
In bifunctional dehydrogenase-cyclohydrolase enzymes, the cyclohydrolase activity is rate-limiting for the overall conversion of 10-formyltetrahydrofolate to 5,10-methylenetetrahydrofolate. This makes it a key regulatory point in one-carbon flux.
Allosteric Activation by NADP+
In simple terms: Binding of a cofactor in one part of the enzyme can speed up the cyclohydrolase reaction in another part.
For human NADP+-dependent methylenetetrahydrofolate dehydrogenase/cyclohydrolase, binding of 2',5'-ADP to the dehydrogenase domain stimulates cyclohydrolase activity, demonstrating interdomain communication.
Structural Basis of Catalysis
In simple terms: The 3D structure shows how the enzyme positions the substrate for reaction.
Crystal structures of methenyltetrahydrofolate cyclohydrolase from Methylobacterium extorquens AM1 revealed a molecular mechanism involving a conserved glutamate residue that activates a water molecule for nucleophilic attack.
Key Genes Involved in GO:0004477 methenyltetrahydrofolate cyclohydrolase activity
The following genes encode proteins that possess or are associated with methenyltetrahydrofolate cyclohydrolase activity (GO:0004477).
| Gene | Major Role | Research Relevance |
|---|---|---|
| MTHFD1 | Trifunctional enzyme with dehydrogenase, cyclohydrolase, and synthetase activities in cytoplasm | Provides one-carbon units for purine and thymidylate synthesis; linked to folate-related disorders |
| MTHFD2 | Bifunctional mitochondrial enzyme with dehydrogenase and cyclohydrolase activities | Overexpressed in many cancers; target for inhibitor development |
| MTHFD2L | Bifunctional mitochondrial enzyme with dehydrogenase and cyclohydrolase activities | Compensates for MTHFD2 in some tissues; embryonic development |
| MTHFD1L | Monofunctional synthetase in mitochondria | Produces formate for cytoplasmic one-carbon pool; not directly cyclohydrolase |
| MTHFR | Methylenetetrahydrofolate reductase | Regulates folate cycle; indirect interaction with cyclohydrolase pathway |
| SHMT1 | Serine hydroxymethyltransferase 1 | Generates 5,10-methylene-THF; feeds into cyclohydrolase pathway |
| SHMT2 | Serine hydroxymethyltransferase 2 | Mitochondrial serine metabolism; links to one-carbon flux |
| TYMS | Thymidylate synthase | Consumes 5,10-methylene-THF; downstream of cyclohydrolase |
| GART | Phosphoribosylglycinamide formyltransferase | Uses 10-formyl-THF for purine synthesis; product of cyclohydrolase |
| ATIC | AICAR transformylase | Uses 10-formyl-THF in purine synthesis |
| NUDT5 | Nudix hydrolase 5 | Non-enzymatic role in repressing purine de novo synthesis; may interact with folate metabolism |
| MTHFD2 (isoform) | Mitochondrial cyclohydrolase/dehydrogenase | Structural and kinetic studies |
| MTHFD1 (rat) | Rat liver cyclohydrolase | Biochemical characterization of 5-formyl-THF formation |
| MTHFD (porcine) | Porcine liver trifunctional enzyme | Evidence for common dehydrogenase-cyclohydrolase site |
| MTHFD (human) | Human bifunctional enzyme | Allosteric regulation by NADP+ |
| MTHFD2 (mouse) | Mouse mitochondrial enzyme | Knockout studies show embryonic lethality |
| MTHFD1 (yeast) | Yeast trifunctional enzyme | Model for folate metabolism |
| MTHFD2 (zebrafish) | Zebrafish mitochondrial enzyme | Developmental studies |
How Is methenyltetrahydrofolate cyclohydrolase activity Regulated?
The cyclohydrolase activity of bifunctional enzymes is regulated by allosteric binding of NADP+ to the dehydrogenase domain, which stimulates the cyclohydrolase reaction. Additionally, the overall one-carbon flux is influenced by the expression levels of MTHFD2, which is induced in rapidly proliferating cells and cancers. The rate-limiting nature of the cyclohydrolase step within bifunctional enzymes further underscores its regulatory role.
methenyltetrahydrofolate cyclohydrolase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| MTHFD2 | Cancer proliferation | Knockout in cancer cell lines (e.g., HeLa, MDA-MB-231) |
| MTHFD1 | Neural tube defects, folate deficiency | Knock-in mouse models with SNPs |
| MTHFD2L | Embryonic lethality in mice | Conditional knockout mice |
| NUDT5 | Purine synthesis regulation | Overexpression and knockout in HEK293 |
| MTHFD2 | Structural studies | Point mutations in catalytic residues |
Cancer Metabolism
MTHFD2, which possesses methenyltetrahydrofolate cyclohydrolase activity, is overexpressed in many cancers and supports proliferation by maintaining one-carbon units for nucleotide synthesis. Targeting this activity is a potential therapeutic strategy.
Folate-Related Disorders
Mutations in MTHFD1, which includes cyclohydrolase activity, have been associated with increased risk of neural tube defects and other folate-related pathologies.
Mitochondrial One-Carbon Metabolism
MTHFD2L and MTHFD2 are critical for mitochondrial one-carbon metabolism, and their dysfunction can affect embryonic development and cellular stress responses.
From methenyltetrahydrofolate cyclohydrolase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of MTHFD2 cyclohydrolase activity impair cancer growth? | MTHFD2 knockout in cancer cell lines |
| What is the catalytic mechanism of cyclohydrolase? | Point mutations in active site residues (e.g., Glu) |
| How does NADP+ binding regulate cyclohydrolase? | Knock-in of allosteric site mutations |
| What is the role of MTHFD1 in development? | Conditional knockout mouse |
| Can we tag the enzyme for localization studies? | Knock-in of FLAG or GFP tag |
| Does overexpression of MTHFD2 drive proliferation? | Overexpression in cell lines |
How to Study the methenyltetrahydrofolate cyclohydrolase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Spectrophotometric assay | Cyclohydrolase activity | Kinetic studies and inhibitor screening |
| X-ray crystallography | 3D structure | Mechanistic insights and drug design |
| LC-MS metabolomics | Folate metabolite levels | Pathway flux analysis |
| CRISPR knockout screen | Gene essentiality | Identify synthetic lethal partners |
| Western blot | Protein expression | Validate knockout/overexpression |
| qRT-PCR | mRNA levels | Gene expression analysis |
| Immunofluorescence | Subcellular localization | Mitochondrial vs cytoplasmic localization |
Enzymatic Assays
Cyclohydrolase activity can be measured spectrophotometrically by monitoring the conversion of 5,10-methenyltetrahydrofolate to 10-formyltetrahydrofolate at 350 nm. This method is used to determine kinetic parameters and inhibitor efficacy.
Structural Biology
X-ray crystallography and cryo-EM can resolve the structure of cyclohydrolase domains, revealing substrate binding and catalytic residues. These studies inform inhibitor design.
Metabolomics
LC-MS-based metabolomics quantifies folate species and one-carbon metabolites, providing a readout of cyclohydrolase activity in cells.
CRISPR Screening
Genome-wide CRISPR knockout screens can identify genes that modulate sensitivity to cyclohydrolase inhibition, uncovering synthetic lethal interactions.
How CRISPR Can Be Used to Study GO:0004477 methenyltetrahydrofolate cyclohydrolase activity
Knockout
CRISPR-Cas9 knockout of MTHFD2 or MTHFD1 can abolish cyclohydrolase activity, leading to impaired proliferation in cancer cells and altered one-carbon flux. These models are used to study the essentiality of the activity.
Point Mutation
Introducing point mutations in catalytic residues (e.g., glutamate) of the cyclohydrolase domain via CRISPR can dissect the enzymatic contribution separate from other domains.
Knock-in
Knock-in of tagged versions (e.g., FLAG, GFP) allows for affinity purification and localization studies of the cyclohydrolase enzyme.
Overexpression
CRISPR activation (CRISPRa) or lentiviral overexpression of MTHFD2 can model the elevated cyclohydrolase activity observed in cancers, enabling studies on proliferation and drug resistance.
How EDITGENE Supports methenyltetrahydrofolate cyclohydrolase activity Research
Researchers studying methenyltetrahydrofolate cyclohydrolase activity-related genes often need to determine whether a candidate gene is causally involved in one-carbon metabolism, cancer proliferation, or developmental processes. EDITGENE provides comprehensive CRISPR-based services to create precise cellular and animal models for such investigations.
Contact EDITGENE today to design your custom CRISPR model for methenyltetrahydrofolate cyclohydrolase activity research.
Frequently Asked Questions About methenyltetrahydrofolate cyclohydrolase activity
What is methenyltetrahydrofolate cyclohydrolase activity?
It is the enzymatic activity (GO:0004477) that catalyzes the hydrolysis of 5,10-methenyltetrahydrofolate to 10-formyltetrahydrofolate, a key step in one-carbon metabolism.
What genes are involved in methenyltetrahydrofolate cyclohydrolase activity?
Genes include MTHFD1, MTHFD2, and MTHFD2L, which encode bifunctional or trifunctional enzymes containing this activity.
What is the reaction catalyzed by GO:0004477?
5,10-methenyltetrahydrofolate + H2O = 10-formyltetrahydrofolate.
Why is methenyltetrahydrofolate cyclohydrolase activity important in cancer?
MTHFD2, which has this activity, is overexpressed in many cancers to support nucleotide synthesis and proliferation, making it a drug target.
How is methenyltetrahydrofolate cyclohydrolase activity regulated?
It can be allosterically stimulated by NADP+ binding to the dehydrogenase domain of bifunctional enzymes.
What diseases are associated with mutations in MTHFD1?
MTHFD1 mutations have been linked to neural tube defects and folate-related disorders.
How can I study methenyltetrahydrofolate cyclohydrolase activity in the lab?
Enzymatic assays, metabolomics, and CRISPR knockout models are common approaches.
What is the rate-limiting step in bifunctional dehydrogenase-cyclohydrolase enzymes?
The cyclohydrolase step is often rate-limiting for the conversion of 10-formyltetrahydrofolate to 5,10-methylenetetrahydrofolate.
Are there structural insights into methenyltetrahydrofolate cyclohydrolase?
Yes, crystal structures have revealed a conserved glutamate residue involved in catalysis.
What CRISPR models are available for studying GO:0004477?
Knockout, point mutation, knock-in, and overexpression models can be generated for genes like MTHFD2.
Conclusion
Methenyltetrahydrofolate cyclohydrolase activity (GO:0004477) is a fundamental enzymatic step in one-carbon metabolism, bridging folate species essential for nucleotide synthesis and methylation. Its presence in multifunctional enzymes like MTHFD1 and MTHFD2 underscores its integration into cellular metabolism, with significant implications for cancer and developmental disorders. Continued research using advanced CRISPR models and structural biology will further illuminate its mechanistic and therapeutic potential.
References
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- 7. Baggott JE et al.. 2003. 5,10-methenyltetrahydrofolate cyclohydrolase, rat liver and chemically catalysed formation of 5-formyltetrahydrofolate.. Biochem J 374(Pt 3):773-8 PMID: 12793858
- 8. Drummond D et al.. 1983. Methylenetetrahydrofolate dehydrogenase - methenyltetrahydrofolate cyclohydrolase - formyltetrahydrofolate synthetase from porcine liver: evidence to support a common dehydrogenase-cyclohydrolase site.. Can J Biochem Cell Biol 61(11):1166-71 PMID: 6607769
