GO:0004441 inositol-1,4-bisphosphate 1-phosphatase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0004441 describes the enzymatic activity that removes a phosphate from 1D-myo-inositol 1,4-bisphosphate to produce 1D-myo-inositol 4-phosphate and free phosphate.
• The enzyme is a lithium-sensitive inositol polyphosphate 1-phosphatase that also acts on other inositol polyphosphates, including inositol 1,3,4-trisphosphate and inositol 1,4,5-trisphosphate.
• Its activity is inhibited by lithium, calcium and manganese, linking it to mood-stabilizer pharmacology and phosphoinositide signaling.
• Structural studies of the enzyme from bovine brain and Entamoeba histolytica have defined the catalytic fold and substrate-binding residues.
• In fission yeast, the Asp1 protein carries a [2Fe-2S] cluster that inhibits its inositol pyrophosphate 1-phosphatase activity, showing redox-linked regulation.
• Dysregulation of inositol polyphosphate phosphatases is implicated in cancer, neurodegeneration and metabolic signaling, making this activity a target for functional genomics.
Description
Inositol-1,4-bisphosphate 1-phosphatase activity (GO:0004441) is a molecular function that catalyzes the hydrolysis of 1D-myo-inositol 1,4-bisphosphate to 1D-myo-inositol 4-phosphate and inorganic phosphate. This reaction is part of the phosphoinositide signaling network, where inositol polyphosphates act as second messengers and metabolic intermediates. The enzyme was first purified from rat liver and calf brain, where it was shown to be a lithium-sensitive phosphatase with broad specificity for inositol polyphosphates. Researchers study GO:0004441 because it controls the levels of signaling lipids and soluble inositol phosphates that influence cell growth, secretion and neuronal function. The activity is also a key target of lithium, a drug used in bipolar disorder, which inhibits the enzyme and alters inositol phosphate turnover. Structural and biochemical work has revealed that the enzyme belongs to a distinct family of metal-dependent phosphatases with a catalytic core that binds inositol phosphates and divalent cations. In this article, we summarize the definition, mechanism, key genes, disease links and experimental models for studying GO:0004441, with a focus on CRISPR-based approaches for functional validation.
inositol-1,4-bisphosphate 1-phosphatase activity At A Glance
| GO ID | GO:0004441 |
|---|---|
| GO term | inositol-1,4-bisphosphate 1-phosphatase activity |
| Ontology | molecular_function |
| Synonym | 1D-myo-inositol-1,4-bisphosphate 1-phosphohydrolase activity; inositol polyphosphate 1-phosphatase activity; inositol-polyphosphate 1-phosphatase activity |
| Major function | Hydrolyzes 1D-myo-inositol 1,4-bisphosphate to 1D-myo-inositol 4-phosphate and phosphate |
| Substrate specificity | Acts on inositol 1,4-bisphosphate and other inositol polyphosphates such as inositol 1,3,4-trisphosphate and inositol 1,4,5-trisphosphate |
| Inhibitors | Lithium, calcium and manganese inhibit the enzyme |
| Cofactor | Divalent metal ions are required for catalysis; the enzyme is inhibited by high Ca2+ and Mn2+ |
| Structural fold | Belongs to a metal-dependent phosphatase family with a catalytic domain that binds inositol phosphates |
What Is GO:0004441?
GO:0004441 is defined as the catalysis of the reaction: 1D-myo-inositol 1,4-bisphosphate + H2O = 1D-myo-inositol 4-phosphate + phosphate. In other words, it is the enzymatic removal of the phosphate group at position 1 of inositol 1,4-bisphosphate, leaving inositol 4-phosphate and free phosphate. The activity is also known as inositol polyphosphate 1-phosphatase, reflecting its ability to dephosphorylate several inositol polyphosphates at the 1-position.
Why Is inositol-1,4-bisphosphate 1-phosphatase activity Important in Cell Biology?
GO:0004441 is important because it controls the cellular levels of inositol polyphosphates, which are central to phosphoinositide signaling, calcium mobilization and membrane trafficking. The enzyme is a direct target of lithium, a first-line treatment for bipolar disorder, and its inhibition contributes to the therapeutic and side effects of the drug. In addition, inositol polyphosphate phosphatases are implicated in cancer progression and metabolic regulation, making this activity a potential drug target and a biomarker for signaling studies.
• Regulates inositol polyphosphate pools that act as second messengers in G-protein-coupled receptor signaling.
• Is inhibited by lithium, linking it to the mechanism of action of mood stabilizers.
• Modulates inositol 1,4,5-trisphosphate levels, which control intracellular calcium release.
• Contributes to phosphoinositide turnover and membrane lipid homeostasis.
• Its structural family provides a template for designing selective inhibitors.
• Redox regulation via a [2Fe-2S] cluster in yeast Asp1 links the activity to cellular redox state.
• Dysregulation of inositol polyphosphate phosphatases is associated with cancer and transformation.
• Provides a biochemical marker for lithium response in research models.
• Enables functional genomics studies of inositol phosphate metabolism using CRISPR screens.
• Serves as a model for understanding metal-dependent phosphatase mechanisms.
Molecular Mechanism of inositol-1,4-bisphosphate 1-phosphatase activity
Substrate binding and specificity
In simple terms: The enzyme grabs inositol 1,4-bisphosphate and positions it for phosphate removal.
The enzyme binds 1D-myo-inositol 1,4-bisphosphate in a catalytic pocket that recognizes the inositol ring and the 4-phosphate group, while the 1-phosphate is positioned for hydrolysis. It also accepts other inositol polyphosphates such as inositol 1,3,4-trisphosphate and inositol 1,4,5-trisphosphate, indicating a broad specificity for the 1-position.
Catalytic mechanism and metal dependence
In simple terms: Metal ions help break the phosphate bond.
Catalysis requires divalent metal ions, and the reaction proceeds via a metal-activated water molecule that attacks the phosphate group. The enzyme is inhibited by high concentrations of calcium and manganese, suggesting that metal ion homeostasis regulates its activity.
Lithium inhibition
In simple terms: Lithium blocks the enzyme, which changes inositol phosphate levels.
Lithium is a potent uncompetitive inhibitor of inositol polyphosphate 1-phosphatase, and this inhibition leads to accumulation of inositol 4,5-bisphosphate in stimulated tissues. This effect is thought to contribute to the therapeutic action of lithium in bipolar disorder.
Structural basis of catalysis
In simple terms: The 3D structure shows how the enzyme holds the substrate and metals.
Crystal structures of the enzyme from bovine brain at 2.3 Å resolution revealed a two-domain architecture with a catalytic cleft containing conserved residues for metal binding and phosphate hydrolysis. Structural analysis of the Entamoeba histolytica enzyme further identified key substrate-binding residues and provided a framework for understanding the catalytic mechanism.
Redox regulation by an iron-sulfur cluster
In simple terms: In yeast, an iron-sulfur cluster can switch the enzyme off.
The Schizosaccharomyces pombe Asp1 protein binds a [2Fe-2S] cluster that inhibits its inositol pyrophosphate 1-phosphatase activity, demonstrating a redox-sensitive regulatory mechanism.
Key Genes Involved in GO:0004441 inositol-1,4-bisphosphate 1-phosphatase activity
The following genes and proteins are directly associated with inositol-1,4-bisphosphate 1-phosphatase activity or its regulation, based on published biochemical and structural studies.
| Gene | Major Role | Research Relevance |
|---|---|---|
| INPP1 | Encodes inositol polyphosphate 1-phosphatase, the enzyme that catalyzes GO:0004441 | Target for lithium response and phosphoinositide signaling studies |
| INPP4A | Inositol polyphosphate 4-phosphatase, related family member | Regulates PI(3)K/Akt signaling and cellular transformation |
| INPP4B | Inositol polyphosphate 4-phosphatase type II | Tumor suppressor in breast and other cancers |
| ITPK1 | Inositol-tetrakisphosphate 1-kinase, produces substrates for 1-phosphatase | Links inositol phosphate metabolism to signaling |
| IPPK | Inositol-pentakisphosphate 2-kinase | Generates higher inositol polyphosphates |
| PPIP5K1 | Diphosphoinositol pentakisphosphate kinase 1 | Produces inositol pyrophosphates that can be dephosphorylated |
| PPIP5K2 | Diphosphoinositol pentakisphosphate kinase 2 | Regulates inositol pyrophosphate levels |
| ASP1 | Fission yeast inositol pyrophosphate 1-phosphatase with a [2Fe-2S] cluster | Model for redox regulation of the activity |
| PLCβ1 | Phospholipase C beta 1, generates inositol 1,4,5-trisphosphate | Upstream of 1-phosphatase substrates |
| PLCγ1 | Phospholipase C gamma 1 | Links receptor tyrosine kinases to inositol phosphate turnover |
| GNAQ | G protein subunit alpha q, activates PLCβ | Controls inositol phosphate production |
| PIP5K1A | Phosphatidylinositol-4-phosphate 5-kinase type 1 alpha | Synthesizes PIP2, precursor of inositol phosphates |
| SYNJ1 | Synaptojanin 1, inositol 5-phosphatase | Regulates phosphoinositide turnover in neurons |
| OCRL | OCRL inositol polyphosphate 5-phosphatase | Mutations cause Lowe syndrome, linked to inositol phosphate metabolism |
| INPP5A | Inositol polyphosphate 5-phosphatase A | Modulates inositol 1,4,5-trisphosphate levels |
| INPP5B | Inositol polyphosphate 5-phosphatase B | Involved in phosphoinositide signaling |
| FIG4 | Phosphoinositide 5-phosphatase, regulates PI(3,5)P2 | Linked to neurodegeneration |
| MTM1 | Myotubularin 1, phosphoinositide phosphatase | Mutations cause myotubular myopathy |
How Is inositol-1,4-bisphosphate 1-phosphatase activity Regulated?
The activity of inositol-1,4-bisphosphate 1-phosphatase is regulated by several mechanisms. Lithium, calcium and manganese inhibit the enzyme, with lithium acting as an uncompetitive inhibitor that binds to the enzyme-substrate complex. In fission yeast, the Asp1 protein is regulated by a [2Fe-2S] cluster that inhibits its 1-phosphatase activity in a redox-dependent manner. Additionally, the enzyme's activity is influenced by substrate availability, which depends on upstream phospholipase C and inositol phosphate kinases. These regulatory layers allow the cell to fine-tune inositol polyphosphate levels in response to extracellular signals and metabolic state.
inositol-1,4-bisphosphate 1-phosphatase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| INPP1 | Bipolar disorder, lithium response | Knockout and point-mutation cell lines for lithium sensitivity assays |
| INPP4A | Cancer, PI(3)K/Akt signaling | Overexpression and knockout models in cancer cell lines |
| INPP4B | Breast cancer, tumor suppression | Knockout and knock-in models for transformation assays |
| OCRL | Lowe syndrome | Patient-derived iPSCs and knockout cell lines |
| FIG4 | Charcot-Marie-Tooth disease | Knockout and point-mutation models in neuronal cells |
Bipolar disorder and lithium response
Inositol polyphosphate 1-phosphatase is a key target of lithium, a mood stabilizer used in bipolar disorder. Lithium inhibits the enzyme, leading to altered inositol phosphate turnover that is thought to contribute to its therapeutic effects. Studies in airways smooth muscle showed that lithium-sensitive 1-phosphatase activity regulates inositol 4,5-bisphosphate accumulation, providing a mechanistic link to lithium action.
Cancer and cell transformation
Inositol polyphosphate phosphatases, including family members related to GO:0004441, regulate PI(3)K/Akt signaling and cellular transformation. Inositol polyphosphate 4-phosphatase-1 (INPP4A) was shown to modulate Akt signaling and transformation, suggesting that dysregulation of inositol phosphate phosphatases can promote oncogenesis.
Neurological and developmental disorders
Phosphoinositide phosphatases such as OCRL, FIG4 and MTM1 are linked to neurological and developmental disorders, including Lowe syndrome, Charcot-Marie-Tooth disease and myotubular myopathy. Although these enzymes act on different inositol lipids, they highlight the broader importance of inositol phosphate metabolism in neuronal function and development.
From inositol-1,4-bisphosphate 1-phosphatase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of INPP1 alter inositol phosphate levels? | INPP1 knockout cell line |
| Does a specific point mutation abolish phosphatase activity? | Point-mutation knock-in of catalytic residues |
| Does lithium sensitivity depend on INPP1 expression? | INPP1 overexpression and knockout cells treated with lithium |
| How does INPP1 affect downstream calcium signaling? | Knockout cells with calcium imaging |
| Does INPP1 regulate Akt signaling? | Knockout and overexpression in cancer cell lines |
| Can we identify new regulators of inositol phosphate metabolism? | CRISPR library screening with inositol phosphate reporters |
How to Study the inositol-1,4-bisphosphate 1-phosphatase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Radiolabeled phosphatase assay | Enzymatic release of phosphate from inositol 1,4-bisphosphate | Kinetic analysis and inhibitor testing |
| X-ray crystallography | Three-dimensional structure of the enzyme | Mechanistic studies and inhibitor design |
| CRISPR knockout | Loss-of-function phenotype | Testing gene function in signaling |
| CRISPR knock-in | Introduction of specific mutations | Structure-function analysis of catalytic residues |
| Mass spectrometry | Inositol polyphosphate levels | Metabolic profiling |
| Calcium imaging | Intracellular calcium release | Downstream signaling assays |
| Western blot | Protein expression and phosphorylation | Akt signaling studies |
| RNA-seq | Transcriptional changes | Pathway analysis after gene editing |
Biochemical phosphatase assays
Enzymatic activity of inositol-1,4-bisphosphate 1-phosphatase can be measured using radiolabeled inositol 1,4-bisphosphate and separation of products by chromatography, as described in early purification studies. These assays are used to determine kinetic parameters and inhibitor sensitivity, including lithium, calcium and manganese.
Structural biology
X-ray crystallography has been used to solve the structure of the enzyme from bovine brain and Entamoeba histolytica, revealing the catalytic fold and substrate-binding residues. These structures guide mutagenesis and inhibitor design.
CRISPR-based functional genomics
CRISPR knockout and knock-in screens can be used to test the role of INPP1 and related genes in inositol phosphate signaling and cell growth. Libraries targeting phosphatases can identify modifiers of lithium sensitivity or Akt signaling.
Metabolite profiling
Mass spectrometry and HPLC-based methods can quantify inositol polyphosphates in cells and tissues, allowing researchers to link enzyme activity to metabolic changes.
How CRISPR Can Be Used to Study GO:0004441 inositol-1,4-bisphosphate 1-phosphatase activity
Knockout
CRISPR knockout of INPP1 can eliminate inositol-1,4-bisphosphate 1-phosphatase activity, allowing researchers to measure changes in inositol phosphate levels and downstream signaling. Knockout cell lines are useful for testing lithium sensitivity and calcium mobilization.
Point Mutation
Point mutations in catalytic residues of INPP1 can be introduced to dissect the enzymatic mechanism and separate phosphatase activity from other functions. Such models help validate structural predictions and identify essential residues.
Knock-in
Knock-in of tagged INPP1 allows for affinity purification and localization studies, while knock-in of disease-associated variants can model altered enzyme function. These models are valuable for studying protein interactions and trafficking.
Overexpression
Overexpression of INPP1 or related phosphatases can suppress inositol phosphate signaling and alter cell growth, providing a gain-of-function complement to knockout studies. Overexpression models are used to test dose-dependent effects on Akt signaling and transformation.
How EDITGENE Supports inositol-1,4-bisphosphate 1-phosphatase activity Research
Researchers studying inositol-1,4-bisphosphate 1-phosphatase activity-related genes often need to determine whether a candidate gene is causally involved in inositol phosphate metabolism, lithium response or cancer signaling. EDITGENE provides a comprehensive suite of CRISPR services to generate precisely engineered cell models for functional validation of GO:0004441 and its associated genes.
Contact EDITGENE today to design your custom CRISPR model for inositol-1,4-bisphosphate 1-phosphatase activity research.
Frequently Asked Questions About inositol-1,4-bisphosphate 1-phosphatase activity
What is inositol-1,4-bisphosphate 1-phosphatase activity?
It is the enzymatic activity that removes a phosphate from inositol 1,4-bisphosphate to produce inositol 4-phosphate and phosphate, encoded by GO:0004441.
What genes are involved in inositol-1,4-bisphosphate 1-phosphatase activity?
The main gene is INPP1, which encodes inositol polyphosphate 1-phosphatase; related genes include INPP4A, INPP4B and ITPK1.
What is the reaction catalyzed by GO:0004441?
The reaction is 1D-myo-inositol 1,4-bisphosphate + H2O = 1D-myo-inositol 4-phosphate + phosphate.
How is inositol-1,4-bisphosphate 1-phosphatase activity inhibited?
It is inhibited by lithium, calcium and manganese, with lithium acting as an uncompetitive inhibitor.
What is the structure of inositol polyphosphate 1-phosphatase?
Crystal structures show a two-domain protein with a catalytic cleft containing metal-binding and substrate-binding residues.
Is inositol-1,4-bisphosphate 1-phosphatase activity linked to disease?
Yes, it is a target of lithium in bipolar disorder and related phosphatases are implicated in cancer and neurological disorders.
How can I study GO:0004441 in the lab?
You can use biochemical phosphatase assays, structural biology, CRISPR knockout or knock-in models, and metabolite profiling.
What is the role of lithium in inositol phosphate signaling?
Lithium inhibits inositol polyphosphate 1-phosphatase, leading to accumulation of inositol 4,5-bisphosphate and altered signaling.
What model organisms are used to study this activity?
The enzyme has been studied in rat liver, calf brain, Entamoeba histolytica and Schizosaccharomyces pombe.
Can CRISPR be used to study inositol-1,4-bisphosphate 1-phosphatase activity?
Yes, CRISPR knockout, point mutation, knock-in and overexpression models enable functional studies of INPP1 and related genes.
Conclusion
GO:0004441, inositol-1,4-bisphosphate 1-phosphatase activity, is a well-characterized enzymatic function that regulates inositol polyphosphate signaling and is a key target of lithium. Its structural and biochemical properties have been defined through decades of research, and its links to cancer and neurological disorders make it a compelling subject for functional genomics. CRISPR-based models offer powerful tools to dissect the role of INPP1 and related genes in health and disease. EDITGENE provides end-to-end services to generate these models and accelerate discovery in inositol phosphate biology.
References
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- 4. Inhorn RC et al.. 1987. Inositol polyphosphate 1-phosphatase from calf brain. Purification and inhibition by Li+, Ca2+, and Mn2+.. J Biol Chem 262(33):15946-52 PMID: 2824473
- 5. Wang H et al.. 2015. Asp1 from Schizosaccharomyces pombe binds a [2Fe-2S](2+) cluster which inhibits inositol pyrophosphate 1-phosphatase activity.. Biochemistry 54(42):6462-74 PMID: 26422458
- 6. Lynch BJ et al.. 1997. [3H]inositol polyphosphate metabolism in muscarinic cholinoceptor-stimulated airways smooth muscle: accumulation of [3H]inositol 4,5 bisphosphate via a lithium-sensitive inositol polyphosphate 1-phosphatase.. J Pharmacol Exp Ther 280(2):974-82 PMID: 9023314
- 7. Ivetac I et al.. 2009. Regulation of PI(3)K/Akt signalling and cellular transformation by inositol polyphosphate 4-phosphatase-1.. EMBO Rep 10(5):487-93 PMID: 19325558
- 8. York JD et al.. 1994. Crystal structure of inositol polyphosphate 1-phosphatase at 2.3-A resolution.. Biochemistry 33(45):13164-71 PMID: 7947723
