GO:0047326 inositol-1,3,4,6-tetrakisphosphate 5-kinase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0047326 defines the enzymatic activity that converts 1D-myo-inositol 1,3,4,6-tetrakisphosphate to 1D-myo-inositol 1,3,4,5,6-pentakisphosphate using ATP.
• The human enzyme responsible for this activity is a homolog of the rat inositol phosphate multikinase, also known as IPMK.
• This 5-kinase step is part of the inositol phosphate phosphorylation pathway that generates higher inositol polyphosphates.
• The reaction was first identified in liver and parotid acinar cell preparations, where it contributes to agonist-stimulated inositol phosphate turnover.
• Studying GO:0047326 helps researchers understand how cells produce inositol pentakisphosphate and related signaling molecules.
• CRISPR-based models (knockout, point mutation, knock-in, overexpression) enable causal testing of this activity in disease and cell signaling research.
Description
Inositol-1,3,4,6-tetrakisphosphate 5-kinase activity (GO:0047326) is a molecular function that catalyzes the ATP-dependent phosphorylation of 1D-myo-inositol 1,3,4,6-tetrakisphosphate to form 1D-myo-inositol 1,3,4,5,6-pentakisphosphate. This reaction is a key step in the complex network of inositol phosphate metabolism, which produces signaling molecules involved in diverse cellular processes. The activity was initially characterized in biochemical studies of liver and parotid acinar cells, where it was shown to participate in the sequential phosphorylation of inositol trisphosphates and tetrakisphosphates. The human enzyme that carries out this reaction was later identified as a homolog of the rat inositol phosphate multikinase, providing a molecular handle for genetic and pharmacological studies. Understanding GO:0047326 is therefore important for researchers investigating inositol signaling, cellular regulation, and the roles of higher inositol polyphosphates in health and disease.
inositol-1,3,4,6-tetrakisphosphate 5-kinase activity At A Glance
| GO ID | GO:0047326 |
|---|---|
| GO term | inositol-1,3,4,6-tetrakisphosphate 5-kinase activity |
| Ontology | molecular_function |
| Synonym | 1D-myo-inositol-tetrakisphosphate 5-kinase activity; ATP:1D-myo-inositol-1,3,4,6-tetrakisphosphate 5-phosphotransferase activity; inositol 1,3,4,6-tetrakisphosphate 5-kinase activity; inositol tetrakisphosphate 5-kinase activity; inositol-tetrakisphosphate 5-kinase activity |
| Major function | Catalyzes the phosphorylation of 1D-myo-inositol 1,3,4,6-tetrakisphosphate to 1D-myo-inositol 1,3,4,5,6-pentakisphosphate using ATP |
| Reaction | 1D-myo-inositol 1,3,4,6-tetrakisphosphate + ATP = 1D-myo-inositol 1,3,4,5,6-pentakisphosphate + ADP + H+ |
| Human enzyme | Homolog of rat inositol phosphate multikinase (IPMK) |
| Pathway context | Part of inositol phosphate phosphorylation pathway in liver and parotid acinar cells |
What Is GO:0047326?
GO:0047326 describes the catalytic activity of an enzyme that transfers a phosphate group from ATP to 1D-myo-inositol 1,3,4,6-tetrakisphosphate, producing 1D-myo-inositol 1,3,4,5,6-pentakisphosphate, ADP, and a proton. In other words, it is a 5-kinase that adds a phosphate at the 5-position of the inositol ring of a specific tetrakisphosphate substrate. This activity is part of the broader inositol phosphate phosphorylation pathway and is distinct from other inositol kinases that act on different substrates or at different positions.
Why Is inositol-1,3,4,6-tetrakisphosphate 5-kinase activity Important in Cell Biology?
GO:0047326 is important because it represents a specific enzymatic step in the generation of higher inositol polyphosphates, which are signaling molecules implicated in many cellular processes. The reaction product, 1D-myo-inositol 1,3,4,5,6-pentakisphosphate, is a precursor for further phosphorylated inositols and can influence cellular signaling and regulation. Studying this activity helps clarify how cells control inositol phosphate flux and how perturbations in this pathway may contribute to disease.
• Defines a key phosphorylation step in inositol phosphate metabolism.
• Produces 1D-myo-inositol 1,3,4,5,6-pentakisphosphate, a signaling molecule.
• Enzyme activity was first identified in liver and parotid acinar cells, linking it to agonist-stimulated signaling.
• Human IPMK homolog provides a genetic target for functional studies.
• Relevant to understanding cellular responses to agonists that trigger inositol phosphate turnover.
• Provides a basis for CRISPR-based dissection of inositol signaling pathways.
• May inform research on diseases involving dysregulated inositol phosphate signaling.
• Supports biochemical and genetic studies of enzyme specificity and regulation.
Molecular Mechanism of inositol-1,3,4,6-tetrakisphosphate 5-kinase activity
Substrate recognition and binding
In simple terms: The enzyme must first grab the correct inositol tetrakisphosphate molecule.
The 5-kinase activity specifically recognizes 1D-myo-inositol 1,3,4,6-tetrakisphosphate as its substrate, distinguishing it from other inositol phosphates. This specificity ensures that the phosphate is added at the 5-position of the inositol ring, yielding 1D-myo-inositol 1,3,4,5,6-pentakisphosphate. The human enzyme, a homolog of rat inositol phosphate multikinase, exhibits this 5-kinase activity toward the tetrakisphosphate substrate.
ATP-dependent phosphorylation
In simple terms: The enzyme uses ATP to add a phosphate group to the inositol ring.
The reaction catalyzed by GO:0047326 requires ATP as the phosphate donor, transferring the terminal phosphate to the 5-position of 1D-myo-inositol 1,3,4,6-tetrakisphosphate. This produces 1D-myo-inositol 1,3,4,5,6-pentakisphosphate, ADP, and a proton. The activity is part of a sequential phosphorylation pathway in which inositol trisphosphates are first converted to tetrakisphosphates and then to pentakisphosphates.
Pathway context in cells
In simple terms: This enzyme works as part of a chain of reactions that build larger inositol phosphates.
In liver, the pathway of myo-inositol 1,3,4-trisphosphate phosphorylation involves multiple kinases, including myo-inositol 1,3,4-trisphosphate 6-kinase, myo-inositol 1,3,4-trisphosphate 5-kinase, and myo-inositol 1,3,4,6-tetrakisphosphate 5-kinase. The latter activity corresponds to GO:0047326 and acts downstream of the tetrakisphosphate-forming steps. In agonist-stimulated rat parotid acinar cells, the formation of inositol 1,3,4,6-tetrakisphosphate and its subsequent phosphorylation are regulated, highlighting the physiological relevance of this activity.
Enzyme identity and regulation
In simple terms: The human enzyme that performs this reaction is related to a rat multikinase.
The human homolog of the rat inositol phosphate multikinase was shown to possess inositol 1,3,4,6-tetrakisphosphate 5-kinase activity, providing a molecular identity for GO:0047326 in humans. This enzyme can act on multiple inositol phosphate substrates, but its 5-kinase activity toward the tetrakisphosphate is a defined component of its catalytic repertoire. Regulation of this activity in cells is likely tied to the availability of substrates and the overall flux through inositol phosphate pathways.
Key Genes Involved in GO:0047326 inositol-1,3,4,6-tetrakisphosphate 5-kinase activity
The following genes and proteins are directly or indirectly associated with inositol-1,3,4,6-tetrakisphosphate 5-kinase activity (GO:0047326) based on the verified literature.
| Gene | Major Role | Research Relevance |
|---|---|---|
| IPMK | Human homolog of rat inositol phosphate multikinase; exhibits inositol 1,3,4,6-tetrakisphosphate 5-kinase activity | Central enzyme for GO:0047326; target for knockout and point mutation studies |
| IP6K1 | Inositol hexakisphosphate kinase, acts downstream in inositol polyphosphate pathway | May be studied in context of inositol phosphate flux |
| IP6K2 | Inositol hexakisphosphate kinase, related to higher inositol phosphates | Potential modifier of pathway output |
| ITPK1 | Inositol-tetrakisphosphate 1-kinase, involved in inositol phosphate phosphorylation | Related kinase in the same pathway |
| ITPKA | Inositol-trisphosphate 3-kinase A, produces inositol tetrakisphosphates | Upstream of GO:0047326 substrate |
| ITPKB | Inositol-trisphosphate 3-kinase B, produces inositol tetrakisphosphates | Upstream of GO:0047326 substrate |
| ITPKC | Inositol-trisphosphate 3-kinase C, involved in inositol phosphate metabolism | May influence substrate availability |
| PLCB1 | Phospholipase C beta 1, generates inositol trisphosphates | Upstream of the pathway |
| PLCB2 | Phospholipase C beta 2, generates inositol trisphosphates | Upstream of the pathway |
| PLCB3 | Phospholipase C beta 3, generates inositol trisphosphates | Upstream of the pathway |
| PLCB4 | Phospholipase C beta 4, generates inositol trisphosphates | Upstream of the pathway |
| IPPK | Inositol-pentakisphosphate 2-kinase, acts on inositol pentakisphosphates | Downstream of GO:0047326 product |
| PPIP5K1 | Diphosphoinositol pentakisphosphate kinase 1, further phosphorylates inositol pyrophosphates | Downstream pathway component |
| PPIP5K2 | Diphosphoinositol pentakisphosphate kinase 2, further phosphorylates inositol pyrophosphates | Downstream pathway component |
| MINPP1 | Multiple inositol polyphosphate phosphatase 1, degrades inositol phosphates | May regulate substrate/product levels |
| INPP5A | Inositol polyphosphate-5-phosphatase A, dephosphorylates inositol phosphates | Potential regulator of pathway |
| INPP5B | Inositol polyphosphate-5-phosphatase B, dephosphorylates inositol phosphates | Potential regulator of pathway |
| OCRL | Inositol polyphosphate-5-phosphatase, involved in inositol phosphate turnover | Potential regulator of pathway |
How Is inositol-1,3,4,6-tetrakisphosphate 5-kinase activity Regulated?
The activity of inositol-1,3,4,6-tetrakisphosphate 5-kinase is regulated by the availability of its substrate, 1D-myo-inositol 1,3,4,6-tetrakisphosphate, which is produced through upstream phosphorylation steps in the inositol phosphate pathway. In agonist-stimulated rat parotid acinar cells, the formation of inositol 1,3,4,6-tetrakisphosphate is regulated, suggesting that the 5-kinase step is subject to cellular control mechanisms. The human enzyme, a homolog of rat inositol phosphate multikinase, may also be regulated at the level of expression or post-translational modification, though specific mechanisms are not detailed in the verified literature.
inositol-1,3,4,6-tetrakisphosphate 5-kinase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| IPMK | Inositol phosphate signaling in cancer and metabolism | IPMK knockout cell lines to assess pathway flux |
| ITPK1 | Inositol phosphate metabolism disorders | Point mutation knock-in to alter kinase activity |
| PLCB1 | Signaling defects in neurological disorders | Overexpression of PLCB1 to stimulate pathway |
| MINPP1 | Inositol phosphate accumulation disorders | Knockout of MINPP1 to study substrate levels |
| PPIP5K1 | Inositol pyrophosphate-related diseases | Knock-in of tagged PPIP5K1 for localization studies |
Inositol phosphate signaling in disease
Dysregulation of inositol phosphate metabolism has been linked to various pathological states, and the enzyme responsible for GO:0047326, IPMK, is part of this network. While specific disease associations for this activity are not detailed in the verified literature, the pathway's role in generating signaling molecules suggests potential relevance to disorders involving cell signaling.
Cancer and cell proliferation
Inositol polyphosphates have been implicated in cell growth and survival, and enzymes in this pathway are studied in cancer contexts. However, direct evidence linking GO:0047326 to cancer from the verified citations is limited, and further research is needed.
Neurological and metabolic conditions
Alterations in inositol phosphate signaling have been observed in neurological and metabolic disorders, but the specific contribution of inositol-1,3,4,6-tetrakisphosphate 5-kinase activity remains to be fully defined. The biochemical characterization of this activity in liver and parotid cells provides a foundation for exploring its role in these conditions.
From inositol-1,3,4,6-tetrakisphosphate 5-kinase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of IPMK abolish inositol-1,3,4,6-tetrakisphosphate 5-kinase activity? | IPMK knockout cell line |
| Which residues are required for 5-kinase catalysis? | Point mutation knock-in of IPMK catalytic residues |
| How does the enzyme localize within cells? | Knock-in of fluorescently tagged IPMK |
| Does overexpression of IPMK increase pentakisphosphate levels? | IPMK overexpression cell line |
| How does agonist stimulation affect pathway flux? | Parotid acinar cell models with agonist treatment |
| What is the role of upstream kinases in substrate supply? | Knockout of ITPKA/ITPKB |
How to Study the inositol-1,3,4,6-tetrakisphosphate 5-kinase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| In vitro kinase assay | Enzymatic conversion of tetrakisphosphate to pentakisphosphate | Direct measurement of GO:0047326 activity |
| HPLC separation | Inositol phosphate species | Quantification of substrate and product |
| CRISPR knockout | Loss of gene function | Testing requirement for IPMK in cells |
| Mass spectrometry | Inositol phosphate levels | Metabolomic profiling of pathway |
| Fluorescence microscopy | Enzyme localization | Live-cell imaging of tagged IPMK |
| siRNA knockdown | Reduced gene expression | Complementary loss-of-function studies |
| Agonist stimulation assays | Pathway activation | Studying regulated formation of inositol phosphates |
| Western blot | Protein expression levels | Validating knockout or overexpression |
Biochemical kinase assays
In vitro kinase assays using radiolabeled ATP and 1D-myo-inositol 1,3,4,6-tetrakisphosphate as substrate can directly measure GO:0047326 activity in cell lysates or purified enzyme preparations. These assays typically separate products by HPLC or chromatography to quantify 1D-myo-inositol 1,3,4,5,6-pentakisphosphate formation.
Genetic knockout and knockdown
CRISPR-Cas9 knockout of IPMK or related genes in cell lines allows researchers to test whether the 5-kinase activity is required for specific cellular phenotypes. Knockdown using siRNA can provide complementary evidence, though knockout is preferred for complete loss-of-function studies.
Mass spectrometry and metabolomics
Mass spectrometry-based methods can quantify inositol phosphate species, including the substrate and product of GO:0047326, in cell extracts. This approach enables profiling of pathway flux and detection of changes in response to genetic or pharmacological perturbations.
Live-cell imaging with tagged enzymes
Knock-in of fluorescent protein tags into the endogenous IPMK locus allows visualization of enzyme localization and dynamics in living cells. This method can reveal whether the enzyme relocalizes upon agonist stimulation or other signals.
How CRISPR Can Be Used to Study GO:0047326 inositol-1,3,4,6-tetrakisphosphate 5-kinase activity
Knockout
CRISPR-Cas9 knockout of IPMK can eliminate inositol-1,3,4,6-tetrakisphosphate 5-kinase activity, enabling researchers to test its role in cellular signaling and inositol phosphate production. Knockout cell lines are valuable for assessing whether the activity is required for specific phenotypes, such as agonist-induced responses.
Point Mutation
Introducing point mutations into the catalytic domain of IPMK via CRISPR can dissect the residues required for 5-kinase activity while preserving other functions of the enzyme. Such models help distinguish the specific contribution of GO:0047326 from other activities of the multikinase.
Knock-in
Knock-in of epitope or fluorescent tags into the endogenous IPMK locus allows for tracking of the enzyme's expression and localization without overexpression artifacts. This approach can reveal where the 5-kinase activity operates within the cell.
Overexpression
Overexpression of IPMK in cell lines can increase the flux through the inositol phosphate pathway, potentially elevating 1D-myo-inositol 1,3,4,5,6-pentakisphosphate levels. This model is useful for gain-of-function studies and for testing downstream effects of enhanced 5-kinase activity.
How EDITGENE Supports inositol-1,3,4,6-tetrakisphosphate 5-kinase activity Research
Researchers studying inositol-1,3,4,6-tetrakisphosphate 5-kinase activity-related genes often need to determine whether a candidate gene is causally involved in the pathway, and CRISPR-based models provide a direct way to test this. EDITGENE offers a suite of services to generate such models efficiently.
Contact EDITGENE today to design your custom CRISPR model for inositol-1,3,4,6-tetrakisphosphate 5-kinase activity research.
Frequently Asked Questions About inositol-1,3,4,6-tetrakisphosphate 5-kinase activity
What is inositol-1,3,4,6-tetrakisphosphate 5-kinase activity?
It is a molecular function (GO:0047326) that catalyzes the ATP-dependent phosphorylation of 1D-myo-inositol 1,3,4,6-tetrakisphosphate to 1D-myo-inositol 1,3,4,5,6-pentakisphosphate.
What gene encodes the human enzyme for GO:0047326?
The human homolog of the rat inositol phosphate multikinase (IPMK) exhibits this activity.
What reaction does GO:0047326 catalyze?
It catalyzes: 1D-myo-inositol 1,3,4,6-tetrakisphosphate + ATP = 1D-myo-inositol 1,3,4,5,6-pentakisphosphate + ADP + H+.
Where was this activity first identified?
It was identified in liver and parotid acinar cell preparations as part of inositol phosphate phosphorylation pathways.
What is the product of this enzyme?
The product is 1D-myo-inositol 1,3,4,5,6-pentakisphosphate, a higher inositol polyphosphate.
How is this activity regulated?
It is regulated by substrate availability and upstream pathway flux, as shown in agonist-stimulated parotid acinar cells.
What diseases are linked to this activity?
Direct disease links are not well established, but inositol phosphate signaling is implicated in cancer and metabolic disorders.
How can I study GO:0047326 in the lab?
Biochemical kinase assays, CRISPR knockout of IPMK, and mass spectrometry-based metabolomics are common approaches.
What CRISPR models are available for this pathway?
Knockout, point mutation, knock-in, and overexpression models of IPMK and related genes can be generated.
Why is inositol-1,3,4,6-tetrakisphosphate 5-kinase activity important?
It contributes to the production of signaling inositol polyphosphates and helps regulate cellular responses to agonists.
Conclusion
Inositol-1,3,4,6-tetrakisphosphate 5-kinase activity (GO:0047326) is a defined enzymatic step in inositol phosphate metabolism, catalyzed by the human IPMK homolog and characterized in liver and parotid cell systems. Understanding this activity provides insight into how cells generate higher inositol polyphosphates and how these pathways may be perturbed in disease. CRISPR-based models offer powerful tools to dissect the function of this activity in a physiological context.
References
- 1. Chang SC et al.. 2002. The human homolog of the rat inositol phosphate multikinase is an inositol 1,3,4,6-tetrakisphosphate 5-kinase.. J Biol Chem 277(46):43836-43 PMID: 12223481
- 2. Shears SB. 1989. The pathway of myo-inositol 1,3,4-trisphosphate phosphorylation in liver. Identification of myo-inositol 1,3,4-trisphosphate 6-kinase, myo-inositol 1,3,4-trisphosphate 5-kinase, and myo-inositol 1,3,4,6-tetrakisphosphate 5-kinase.. J Biol Chem 264(33):19879-86 PMID: 2584198
- 3. Hughes PJ et al.. 1989. The regulation of the phosphorylation of inositol 1,3,4-trisphosphate in cell-free preparations and its relevance to the formation of inositol 1,3,4,6-tetrakisphosphate in agonist-stimulated rat parotid acinar cells.. J Biol Chem 264(33):19871-8 PMID: 2555335
