GO:0047325 inositol-3,4,5,6-tetrakisphosphate 1-kinase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0047325 describes the ATP-dependent phosphorylation of 1D-myo-inositol 3,4,5,6-tetrakisphosphate to 1D-myo-inositol 1,3,4,5,6-pentakisphosphate, a central step in inositol polyphosphate biosynthesis.
• The enzyme is bifunctional, acting as both Ins(3,4,5,6)P4 1-kinase and Ins(1,3,4)P3 5/6-kinase, and is encoded by ITPK1 in humans and ITPK4 in Arabidopsis.
• It is not a protein kinase; the catalytic activity is strictly directed toward inositol polyphosphate substrates.
• Enzyme activity is regulated by inositol 1,3,4-trisphosphate, which acts as a modulator of the rat liver enzyme.
• The enzyme adopts an ATP-grasp fold, and structural studies have defined the determinants of substrate specificity.
• Small-molecule inhibitors of inositol-tetrakisphosphate 1-kinase have been biochemically and biophysically characterized, supporting drug-discovery efforts.
Description
Inositol polyphosphates are a family of soluble signaling molecules that regulate diverse cellular processes, including ion channel activity, chromatin remodeling, and mRNA export. The enzyme defined by GO:0047325, inositol-3,4,5,6-tetrakisphosphate 1-kinase, catalyzes the ATP-dependent conversion of 1D-myo-inositol 3,4,5,6-tetrakisphosphate to 1D-myo-inositol 1,3,4,5,6-pentakisphosphate, a reaction that sits at a branch point in inositol polyphosphate metabolism. This activity was first purified from rat liver and shown to be distinct from inositol 1,4,5-trisphosphate 3-kinase. The same polypeptide also displays Ins(1,3,4)P3 5/6-kinase activity, making it a bifunctional enzyme in inositol phosphate synthesis. Because the products of this reaction are precursors to higher inositol pyrophosphates, the enzyme influences a wide range of physiological outputs. Understanding GO:0047325 is therefore essential for researchers studying inositol signaling, phosphate homeostasis, and related disease mechanisms.
inositol-3,4,5,6-tetrakisphosphate 1-kinase activity At A Glance
| GO ID | GO:0047325 |
|---|---|
| GO term | inositol-3,4,5,6-tetrakisphosphate 1-kinase activity |
| Ontology | molecular_function |
| Synonym | 1D-myo-inositol-tetrakisphosphate 1-kinase activity; inositol-trisphosphate 5-kinase activity; inositol-trisphosphate 6-kinase activity; ATP:1D-myo-inositol-3,4,5,6-tetrakisphosphate 1-phosphotransferase activity |
| Major function | Phosphorylates 1D-myo-inositol 3,4,5,6-tetrakisphosphate to 1D-myo-inositol 1,3,4,5,6-pentakisphosphate using ATP |
| Reaction | 1D-myo-inositol 3,4,5,6-tetrakisphosphate + ATP = 1D-myo-inositol 1,3,4,5,6-pentakisphosphate + ADP + H+ |
| Substrate | 1D-myo-inositol 3,4,5,6-tetrakisphosphate; also Ins(1,3,4)P3 as 5/6-kinase |
| Cofactor | Mg2+ (ATP-dependent phosphotransferase) |
| Cellular location | Cytosol (soluble enzyme) |
| Representative gene | ITPK1 (human); ITPK4 (Arabidopsis) |
What Is GO:0047325?
GO:0047325 is a molecular function term describing the catalysis of the reaction: 1D-myo-inositol 3,4,5,6-tetrakisphosphate + ATP = 1D-myo-inositol 1,3,4,5,6-pentakisphosphate + ADP + H+. In other words, the enzyme transfers the gamma-phosphate of ATP onto the 1-position of the inositol ring of Ins(3,4,5,6)P4, generating Ins(1,3,4,5,6)P5. The term is synonymous with inositol-tetrakisphosphate 1-kinase activity and inositol-trisphosphate 5/6-kinase activity, reflecting the enzyme's ability to phosphorylate both tetrakisphosphate and trisphosphate substrates.
Why Is inositol-3,4,5,6-tetrakisphosphate 1-kinase activity Important in Cell Biology?
GO:0047325 is important because it controls the flux of inositol polyphosphates toward higher phosphorylated species that act as signaling molecules. The reaction product, Ins(1,3,4,5,6)P5, is a precursor of inositol pyrophosphates such as IP7, which regulate processes including insulin secretion, telomere length, and DNA repair. The enzyme is also a validated target for chemical biology, as potent inhibitors of Ins(3,4,5,6)P4 1-kinase have been designed and characterized. In plants, the orthologous enzyme is involved in phosphate sensing and inositol phosphate metabolism. Consequently, understanding this activity provides insight into both fundamental cell biology and potential therapeutic interventions.
• Controls the biosynthesis of inositol pentakisphosphate and downstream inositol pyrophosphates.
• Bifunctional enzyme that also phosphorylates Ins(1,3,4)P3, linking multiple inositol phosphate pools.
• Regulated by Ins(1,3,4)P3, providing feedback control of inositol phosphate flux.
• Target of small-molecule inhibitors with potential for drug development.
• Conserved in plants, where it participates in phosphate homeostasis.
• Distinct from protein kinases, highlighting specificity of inositol phosphate signaling.
• Crystal structure reveals ATP-grasp fold and substrate specificity determinants.
• Involved in cellular processes such as ion channel regulation and chromatin remodeling through its products.
What Happens During inositol-3,4,5,6-tetrakisphosphate 1-kinase activity?
Substrate binding and recognition
In simple terms: The enzyme grabs the inositol tetrakisphosphate molecule and ATP.
The enzyme binds 1D-myo-inositol 3,4,5,6-tetrakisphosphate and ATP in a sequential manner. Structural studies of the related inositol 1,3,4-trisphosphate 5/6-kinase have revealed an ATP-grasp fold that accommodates both the nucleotide and the inositol phosphate substrate. The enzyme also accepts Ins(1,3,4)P3 as a substrate, acting as a 5/6-kinase.
Phosphoryl transfer
In simple terms: The enzyme moves a phosphate from ATP onto the inositol ring.
The gamma-phosphate of ATP is transferred to the 1-position of the inositol ring, converting Ins(3,4,5,6)P4 to Ins(1,3,4,5,6)P5. This reaction requires Mg2+ as a cofactor. The enzyme is not a protein kinase; it specifically phosphorylates inositol polyphosphates.
Product release and downstream metabolism
In simple terms: The product is released and can be further converted into other signaling molecules.
The product, 1D-myo-inositol 1,3,4,5,6-pentakisphosphate, is released and can be further phosphorylated to inositol pyrophosphates. The reaction is part of a metabolic network that includes inositol 3,4,5,6-tetrakisphosphate phosphatase activities, as shown in plant mesophyll cells.
Regulation by inositol trisphosphate
In simple terms: Another inositol molecule can turn the enzyme's activity up or down.
The rat liver enzyme is regulated by inositol 1,3,4-trisphosphate, which modulates its activity. This provides a feedback mechanism to balance inositol phosphate pools.
Key Genes Involved in GO:0047325 inositol-3,4,5,6-tetrakisphosphate 1-kinase activity
The following genes and proteins are directly associated with inositol-3,4,5,6-tetrakisphosphate 1-kinase activity or its regulation.
| Gene | Major Role | Research Relevance |
|---|---|---|
| ITPK1 (human) | Encodes inositol-tetrakisphosphate 1-kinase; bifunctional Ins(3,4,5,6)P4 1-kinase/Ins(1,3,4)P3 5/6-kinase | Central to inositol polyphosphate synthesis; target for inhibitor design |
| ITPK4 (Arabidopsis) | Plant ortholog with ATP-grasp fold; outlier in the ITPK family | Model for phosphate sensing and inositol phosphate metabolism |
| ITPKA | Inositol 1,4,5-trisphosphate 3-kinase; distinct from Ins(3,4,5,6)P4 1-kinase | Used to differentiate enzyme activities |
| ITPKB | Inositol 1,4,5-trisphosphate 3-kinase B | Related inositol kinase; comparison of substrate specificity |
| ITPKC | Inositol 1,4,5-trisphosphate 3-kinase C | Related family member |
| IPPK | Inositol pentakisphosphate 2-kinase | Downstream enzyme in inositol pyrophosphate synthesis |
| PPIP5K1 | Diphosphoinositol pentakisphosphate kinase 1 | Produces inositol pyrophosphates from InsP5 |
| PPIP5K2 | Diphosphoinositol pentakisphosphate kinase 2 | Produces inositol pyrophosphates |
| MINPP1 | Multiple inositol polyphosphate phosphatase 1 | Degrades inositol polyphosphates; balances pathway |
| INPP5A | Inositol polyphosphate-5-phosphatase A | Regulates inositol phosphate levels |
| INPP5B | Inositol polyphosphate-5-phosphatase B | Regulates inositol phosphate levels |
| OCRL | Inositol polyphosphate 5-phosphatase | Mutations cause Lowe syndrome; affects inositol phosphate pools |
| SYNJ1 | Synaptojanin 1 | Inositol 5-phosphatase involved in synaptic vesicle recycling |
| IP6K1 | Inositol hexakisphosphate kinase 1 | Produces IP7 from IP6; downstream of InsP5 |
| IP6K2 | Inositol hexakisphosphate kinase 2 | Produces IP7 |
| IP6K3 | Inositol hexakisphosphate kinase 3 | Produces IP7 |
| ITPK1 (rat) | Purified enzyme used for biochemical characterization | Defined regulation by Ins(1,3,4)P3 |
How Is inositol-3,4,5,6-tetrakisphosphate 1-kinase activity Regulated?
The activity of inositol-3,4,5,6-tetrakisphosphate 1-kinase is regulated by its substrate availability and by inositol 1,3,4-trisphosphate, which modulates the rat liver enzyme. Additionally, the enzyme's bifunctional nature allows it to respond to changes in both Ins(3,4,5,6)P4 and Ins(1,3,4)P3 levels. In plants, cell permeabilization studies have identified both the kinase and a phosphatase acting on Ins(3,4,5,6)P4, indicating that metabolic interconversion is tightly controlled.
inositol-3,4,5,6-tetrakisphosphate 1-kinase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| ITPK1 | Cancer (via inositol pyrophosphate pathway) | Knockout in cancer cell lines; inhibitor treatment |
| ITPK1 | Inositol phosphate imbalance | Point mutation of catalytic residues; overexpression |
| ITPK4 | Plant phosphate homeostasis | Arabidopsis knockout and overexpression lines |
| SYNJ1 | Neurodegeneration (Parkinson's-like) | Knockout mouse models; neuronal cell lines |
| OCRL | Lowe syndrome | Patient-derived fibroblasts; CRISPR knock-in of mutations |
Inositol polyphosphates and cancer
Inositol polyphosphates, including the product of GO:0047325, influence cell growth and survival. While direct mutations in ITPK1 are not commonly reported in cancer, the pathway is implicated in tumorigenesis through downstream inositol pyrophosphates that regulate DNA repair and apoptosis. Inhibitors of inositol-tetrakisphosphate 1-kinase are being explored as chemical probes for cancer research.
Neurological disorders
Inositol signaling is critical for neuronal function. Enzymes that regulate inositol polyphosphate levels, such as synaptojanin 1 (SYNJ1), are linked to neurodegenerative diseases. Although GO:0047325 itself has not been directly linked to a specific neurological disorder, its products contribute to the inositol phosphate pool that affects synaptic transmission.
Plant phosphate homeostasis
In plants, the orthologous enzyme AtITPK4 is involved in phosphate sensing and inositol phosphate metabolism. Cell permeabilization studies in mesophyll cells have identified Ins(3,4,5,6)P4 1-kinase activity, linking it to phosphate stress responses.
From inositol-3,4,5,6-tetrakisphosphate 1-kinase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does ITPK1 loss alter inositol polyphosphate levels? | ITPK1 knockout cell lines (e.g., HEK293) |
| What is the effect of catalytic point mutations on enzyme activity? | Point-mutation knock-in of ITPK1 (e.g., D-to-A) |
| Can tagged ITPK1 be used to study localization? | Knock-in of GFP- or FLAG-tagged ITPK1 |
| Does ITPK1 overexpression change cell growth? | Overexpression of ITPK1 in cancer cell lines |
| What is the role of ITPK4 in phosphate sensing? | Arabidopsis ITPK4 knockout and overexpression |
| Can small-molecule inhibitors block ITPK1 in cells? | Treatment of wild-type cells with inhibitors |
How to Study the inositol-3,4,5,6-tetrakisphosphate 1-kinase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Radiolabeled substrate assay | Kinase activity | Enzyme purification and kinetics |
| Cell permeabilization | Inositol phosphate interconversion | Plant mesophyll cells |
| X-ray crystallography | Protein structure | Substrate specificity and fold |
| Surface plasmon resonance | Binding affinity of inhibitors | Inhibitor characterization |
| Mass spectrometry | Inositol polyphosphate levels | Metabolic profiling |
| Site-directed mutagenesis | Catalytic residues | Mechanistic studies |
| CRISPR knockout | Gene function | Loss-of-function studies |
| Overexpression | Gain-of-function | Cellular phenotype |
Enzymatic assays
Inositol-3,4,5,6-tetrakisphosphate 1-kinase activity can be measured using radiolabeled substrates or coupled enzyme assays. Purification from rat liver and subsequent kinetic analysis defined the enzyme's properties. Cell permeabilization studies in plant mesophyll cells identified the kinase activity by monitoring conversion of Ins(3,4,5,6)P4 to Ins(1,3,4,5,6)P5.
Structural biology
Crystal structures of related inositol 1,3,4-trisphosphate 5/6-kinase have revealed the ATP-grasp fold and substrate-binding determinants. These structures guide mutagenesis and inhibitor design.
Inhibitor characterization
Biochemical and biophysical methods, including surface plasmon resonance and isothermal titration calorimetry, have been used to characterize inhibitors of inositol-tetrakisphosphate 1-kinase. Synthetic analogs of inositol polyphosphates have been designed as potent inhibitors.
Metabolic profiling
Mass spectrometry-based profiling of inositol polyphosphates can quantify the products of GO:0047325 in cells and tissues. Such methods have been applied to plant and animal systems.
How CRISPR Can Be Used to Study GO:0047325 inositol-3,4,5,6-tetrakisphosphate 1-kinase activity
Knockout
CRISPR knockout of ITPK1 can eliminate inositol-3,4,5,6-tetrakisphosphate 1-kinase activity, allowing researchers to study its role in inositol polyphosphate synthesis and downstream processes. Knockout cell lines are valuable for validating inhibitor specificity.
Point Mutation
Introducing point mutations in the catalytic domain of ITPK1 (e.g., aspartate to alanine) can abolish kinase activity while preserving protein structure, enabling separation of catalytic and non-catalytic functions.
Knock-in
Knock-in of epitope tags (e.g., FLAG, GFP) at the endogenous ITPK1 locus allows for localization and interaction studies under native expression levels.
Overexpression
Overexpression of ITPK1 or its orthologs can increase flux through the inositol polyphosphate pathway, revealing gain-of-function phenotypes and providing material for biochemical assays.
How EDITGENE Supports inositol-3,4,5,6-tetrakisphosphate 1-kinase activity Research
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Frequently Asked Questions About inositol-3,4,5,6-tetrakisphosphate 1-kinase activity
What is inositol-3,4,5,6-tetrakisphosphate 1-kinase activity?
It is the enzyme activity defined by GO:0047325 that catalyzes the ATP-dependent phosphorylation of 1D-myo-inositol 3,4,5,6-tetrakisphosphate to 1D-myo-inositol 1,3,4,5,6-pentakisphosphate.
What genes are involved in inositol-3,4,5,6-tetrakisphosphate 1-kinase activity?
The primary gene is ITPK1 in humans, which encodes a bifunctional enzyme with both Ins(3,4,5,6)P4 1-kinase and Ins(1,3,4)P3 5/6-kinase activities. In Arabidopsis, ITPK4 is an ortholog.
What is the reaction catalyzed by GO:0047325?
The reaction is: 1D-myo-inositol 3,4,5,6-tetrakisphosphate + ATP = 1D-myo-inositol 1,3,4,5,6-pentakisphosphate + ADP + H+.
Is inositol-3,4,5,6-tetrakisphosphate 1-kinase a protein kinase?
No, it is not a protein kinase; it specifically phosphorylates inositol polyphosphates.
How is inositol-3,4,5,6-tetrakisphosphate 1-kinase regulated?
The enzyme is regulated by inositol 1,3,4-trisphosphate, which modulates its activity in rat liver.
What diseases are associated with inositol-3,4,5,6-tetrakisphosphate 1-kinase activity?
While direct mutations are not common, the pathway is implicated in cancer and neurological disorders through downstream inositol pyrophosphates.
What is the structure of inositol-3,4,5,6-tetrakisphosphate 1-kinase?
The enzyme adopts an ATP-grasp fold, as revealed by crystal structures of related inositol 1,3,4-trisphosphate 5/6-kinase.
Can inositol-3,4,5,6-tetrakisphosphate 1-kinase be inhibited?
Yes, small-molecule inhibitors have been designed and characterized, including D- and L-chiro-inositol 2,3,4,5-tetrakisphosphate analogs.
What model systems are used to study GO:0047325?
Rat liver, plant mesophyll cells, and recombinant expression systems are commonly used.
How can CRISPR help study inositol-3,4,5,6-tetrakisphosphate 1-kinase activity?
CRISPR knockout, point mutation, knock-in, and overexpression models allow precise dissection of gene function and catalytic mechanisms.
Conclusion
GO:0047325, inositol-3,4,5,6-tetrakisphosphate 1-kinase activity, is a key enzymatic step in inositol polyphosphate metabolism, bridging Ins(3,4,5,6)P4 to Ins(1,3,4,5,6)P5 and influencing diverse cellular processes. Its bifunctional nature, regulation by Ins(1,3,4)P3, and conservation across species make it a compelling target for both basic and translational research. With CRISPR-based tools and biochemical assays, researchers can now dissect its roles in health and disease with unprecedented precision.
References
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- 2. Ng MY et al.. 2025. Biochemical and biophysical characterization of inositol-tetrakisphosphate 1-kinase inhibitors.. J Biol Chem 301(3):108274 PMID: 39922495
- 3. Brearley CA et al.. 2000. Metabolic relations of inositol 3,4,5,6-tetrakisphosphate revealed by cell permeabilization. Identification of inositol 3,4,5, 6-tetrakisphosphate 1-kinase and inositol 3,4,5,6-tetrakisphosphate phosphatase activities in mesophyll cells.. Plant Physiol 122(4):1209-16 PMID: 10759517
- 4. Qian X et al.. 2005. The Ins(1,3,4)P3 5/6-kinase/Ins(3,4,5,6)P4 1-kinase is not a protein kinase.. Biochem J 389(Pt 2):389-95 PMID: 15762844
- 5. Craxton A et al.. 1994. Inositol 1,4,5,6-tetrakisphosphate is phosphorylated in rat liver by a 3-kinase that is distinct from inositol 1,4,5-trisphosphate 3-kinase.. J Biol Chem 269(6):4337-42 PMID: 8308002
- 6. Miller GJ et al.. 2005. Specificity determinants in inositol polyphosphate synthesis: crystal structure of inositol 1,3,4-trisphosphate 5/6-kinase.. Mol Cell 18(2):201-12 PMID: 15837423
- 7. Tan Z et al.. 1997. Properties of the inositol 3,4,5,6-tetrakisphosphate 1-kinase purified from rat liver. Regulation of enzyme activity by inositol 1,3,4-trisphosphate.. J Biol Chem 272(4):2285-90 PMID: 8999935
- 8. Sweetman D et al.. 2007. Arabidopsis thaliana inositol 1,3,4-trisphosphate 5/6-kinase 4 (AtITPK4) is an outlier to a family of ATP-grasp fold proteins from Arabidopsis.. FEBS Lett 581(22):4165-71 PMID: 17698066
