GO:0000823 inositol-1,4,5-trisphosphate 6-kinase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0000823 defines the catalytic activity that converts 1D-myo-inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) to 1D-myo-inositol 1,4,5,6-tetrakisphosphate (Ins(1,4,5,6)P4) using ATP.
• The enzyme is also known as inositol polyphosphate multikinase (IpmK) and inositol trisphosphate 6-kinase.
• Ins(1,4,5)P3 6-kinase activity was first biochemically identified in plants and yeast, and later linked to a conserved ATP-grasp fold family.
• This activity is a branch point in inositol polyphosphate metabolism, influencing Ins(1,4,5,6)P4 levels and downstream signaling.
• Dysregulation of inositol polyphosphate kinases has been implicated in cancer, neurodegeneration, and metabolic disorders.
• CRISPR-based knockout, point-mutation, and knock-in models enable precise dissection of GO:0000823 in human cells and model organisms.
Description
Inositol-1,4,5-trisphosphate 6-kinase activity (GO:0000823) is a molecular function that catalyzes the phosphorylation of 1D-myo-inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) at the 6-hydroxyl position to produce 1D-myo-inositol 1,4,5,6-tetrakisphosphate (Ins(1,4,5,6)P4). This reaction consumes ATP and releases ADP and a proton, placing the enzyme within the broader family of inositol polyphosphate kinases that shape cellular phosphoinositide signals. The activity was first described in pea roots as an Ins(1,4,5)P3-6-kinase and subsequently purified from Saccharomyces cerevisiae, where it was named inositol 1,4,5-trisphosphate 6-kinase. In yeast, the enzyme is encoded by IPK2 (also known as ARG82), a founding member of the inositol polyphosphate multikinase (IpmK) family. The same activity is conserved in plants, where Arabidopsis thaliana ITPK4 represents an outlier within the ATP-grasp fold protein family. Researchers study GO:0000823 because it sits at a metabolic branch point: Ins(1,4,5)P3 can be phosphorylated at the 3-position by Ins(1,4,5)P3 3-kinase or at the 6-position by this enzyme, generating distinct tetrakisphosphate isomers with different signaling roles. The product Ins(1,4,5,6)P4 is a precursor for higher inositol polyphosphates and has been linked to regulation of ion channels, chromatin remodeling, and stress responses. Understanding this activity is therefore essential for mapping inositol polyphosphate networks in health and disease.
inositol-1,4,5-trisphosphate 6-kinase activity At A Glance
| GO ID | GO:0000823 |
|---|---|
| GO term | inositol-1,4,5-trisphosphate 6-kinase activity |
| Ontology | molecular_function |
| Synonym | inositol polyphosphate multikinase activity; inositol trisphosphate 6-kinase activity; IpmK |
| Major function | Catalyzes ATP-dependent phosphorylation of Ins(1,4,5)P3 to Ins(1,4,5,6)P4 |
| Reaction | 1D-myo-inositol 1,4,5-trisphosphate + ATP = 1D-myo-inositol 1,4,5,6-tetrakisphosphate + ADP + H+ |
| Substrate | 1D-myo-inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) |
| Product | 1D-myo-inositol 1,4,5,6-tetrakisphosphate (Ins(1,4,5,6)P4) |
| Cofactor | ATP (as phosphate donor); Mg2+ typically required for kinase activity |
| Cellular context | Cytosolic inositol polyphosphate metabolic pathway |
| Representative genes | IPK2 (yeast), ITPK4 (Arabidopsis), IPMK (metazoans) |
What Is GO:0000823?
GO:0000823 describes the catalytic activity of an enzyme that transfers a phosphate group from ATP to the 6-hydroxyl of 1D-myo-inositol 1,4,5-trisphosphate, yielding 1D-myo-inositol 1,4,5,6-tetrakisphosphate, ADP, and a proton. The term is classified as a molecular_function in the Gene Ontology and is synonymous with inositol polyphosphate multikinase activity, inositol trisphosphate 6-kinase activity, and IpmK. This activity is distinct from Ins(1,4,5)P3 3-kinase, which phosphorylates the 3-position and initiates a separate metabolic branch.
Why Is inositol-1,4,5-trisphosphate 6-kinase activity Important in Cell Biology?
GO:0000823 is important because it defines a key enzymatic step that determines the balance between Ins(1,4,5)P3 and Ins(1,4,5,6)P4, two molecules with distinct signaling functions. Ins(1,4,5)P3 is a canonical second messenger that releases calcium from intracellular stores, while Ins(1,4,5,6)P4 can modulate ion channels and serve as a precursor for higher inositol polyphosphates involved in gene regulation and stress responses. The enzyme activity is conserved from plants to humans, and its dysregulation has been associated with cancer cell proliferation, neurodegeneration, and metabolic disease. In yeast, the IpmK enzyme regulates Ins(1,4,5,6)P4 levels and influences arginine metabolism and stress signaling. In plants, ITPK4 is an outlier ATP-grasp fold protein that contributes to inositol polyphosphate diversity. Because the activity sits at a metabolic branch point, small changes in its catalytic efficiency can redirect flux toward different inositol polyphosphate isomers, making it a sensitive node for cellular regulation. Researchers targeting this activity can use CRISPR models to test causal roles in disease and to validate inhibitors such as D- and L-chiro-inositol 2,3,4,5-tetrakisphosphate derivatives.
• Controls the conversion of Ins(1,4,5)P3 to Ins(1,4,5,6)P4, a branch point in inositol polyphosphate signaling.
• Regulates levels of Ins(1,4,5,6)P4, which influences ion channel activity and chromatin-associated processes.
• Conserved from plants to humans, enabling cross-species studies of inositol polyphosphate metabolism.
• Implicated in cancer biology through altered inositol polyphosphate kinase expression.
• Linked to neurodegenerative and metabolic conditions where phosphoinositide signaling is perturbed.
• Provides a target for small-molecule inhibitors such as chiro-inositol tetrakisphosphate analogs.
• Essential for yeast arginine metabolism and stress responses via IpmK.
• Contributes to plant inositol polyphosphate diversity through ITPK4.
• Enables metabolic labeling and tracing studies using 13C-isotopically labeled Ins(1,4,5)P3.
• Supports CRISPR-based functional genomics of inositol polyphosphate pathways.
Molecular Mechanism of inositol-1,4,5-trisphosphate 6-kinase activity
Substrate recognition and binding
In simple terms: The enzyme grabs Ins(1,4,5)P3 and ATP, positioning them for phosphate transfer.
The enzyme binds 1D-myo-inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) as its primary substrate, recognizing the 4,5-bisphosphate motif and the 1-phosphate group. In yeast, purification of the Ins(1,4,5)P3 6-kinase showed strict specificity for Ins(1,4,5)P3 over other inositol phosphates. The enzyme also binds ATP, which serves as the phosphate donor, and typically requires Mg2+ for catalysis. Substrate binding is thought to involve a conserved ATP-grasp fold, as seen in Arabidopsis ITPK4, which is an outlier within this fold family.
Catalytic phosphorylation at the 6-position
In simple terms: A phosphate from ATP is attached to the 6-position of the inositol ring.
The catalytic step transfers the gamma-phosphate of ATP to the 6-hydroxyl of Ins(1,4,5)P3, producing 1D-myo-inositol 1,4,5,6-tetrakisphosphate, ADP, and a proton. This reaction is distinct from 3-kinase activity, which phosphorylates the 3-position and generates Ins(1,3,4,5)P4. In liver, multiple Ins(1,3,4)P3 kinases were identified, including a 6-kinase that acts on Ins(1,3,4)P3, showing that 6-kinase activities can act on multiple inositol trisphosphate isomers. The product Ins(1,4,5,6)P4 is a key node for downstream inositol polyphosphate synthesis.
Product release and metabolic channeling
In simple terms: After making Ins(1,4,5,6)P4, the enzyme releases it for further conversions.
Following catalysis, Ins(1,4,5,6)P4 is released and can be further phosphorylated by other inositol polyphosphate kinases to generate higher inositol pyrophosphates. In Saccharomyces cerevisiae, a novel pathway initiated by Ins(1,4,5)P3 3-kinase activity produces distinct inositol polyphosphates, highlighting the metabolic branching that includes 6-kinase activity. The IpmK enzyme in yeast regulates Ins(1,4,5,6)P4 levels, and its loss alters the balance of inositol polyphosphates. This product release step is critical for maintaining flux through the inositol polyphosphate network.
Regulation by ATP and divalent cations
In simple terms: ATP and magnesium control how fast the enzyme works.
The kinase activity is ATP-dependent, and depletion of ATP reduces Ins(1,4,5,6)P4 production. Divalent cations such as Mg2+ are typically required for kinase catalysis, although the exact metal dependence may vary between species. In plants, the pea root enzyme showed optimal activity under specific pH and ionic conditions, indicating that cellular environment modulates catalysis. In yeast, the purified enzyme displayed Michaelis-Menten kinetics consistent with a typical ATP-dependent kinase.
Inhibition and chemical probes
In simple terms: Synthetic molecules can block this enzyme, helping researchers study its role.
D- and L-chiro-inositol 2,3,4,5-tetrakisphosphate derivatives were designed as potent inhibitors of Ins(3,4,5,6)P4 1-kinase/Ins(1,3,4)P3 5/6-kinase, demonstrating that inositol polyphosphate kinases can be targeted with synthetic analogs. These inhibitors provide tools to dissect the contribution of 6-kinase activity to cellular signaling. Semi-enzymatic synthesis of 13C-isotopically labeled Ins(1,4,5)P3 enables metabolic tracing of this activity in cells. Such probes are valuable for validating CRISPR-generated models of GO:0000823.
Key Genes Involved in GO:0000823 inositol-1,4,5-trisphosphate 6-kinase activity
The following genes and proteins are experimentally linked to inositol-1,4,5-trisphosphate 6-kinase activity or its metabolic network.
| Gene | Major Role | Research Relevance |
|---|---|---|
| IPK2 (yeast) | Encodes inositol polyphosphate multikinase (IpmK) with 6-kinase activity | Model for studying Ins(1,4,5,6)P4 regulation and arginine metabolism |
| ARG82 (yeast) | Alternative name for IPK2; regulates inositol polyphosphate signaling | Links 6-kinase activity to transcriptional and stress responses |
| ITPK4 (Arabidopsis) | Inositol 1,3,4-trisphosphate 5/6-kinase 4; ATP-grasp fold outlier | Plant model for inositol polyphosphate diversity |
| IPMK (human) | Inositol polyphosphate multikinase with 6-kinase activity | Implicated in cancer and neurodegeneration |
| ITPK1 (human) | Inositol-tetrakisphosphate 1-kinase family member | Related inositol phosphate kinase with overlapping substrate specificity |
| ITPKA (human) | Ins(1,4,5)P3 3-kinase | Defines the competing 3-kinase branch |
| ITPKB (human) | Ins(1,4,5)P3 3-kinase B | Regulates Ins(1,3,4,5)P4 production |
| ITPKC (human) | Ins(1,4,5)P3 3-kinase C | Modulates calcium signaling |
| PLC (phospholipase C) | Generates Ins(1,4,5)P3 from PIP2 | Upstream of 6-kinase activity |
| IP5K (human) | Inositol pentakisphosphate 2-kinase | Downstream of Ins(1,4,5,6)P4 |
| PPIP5K (human) | Diphosphoinositol pentakisphosphate kinase | Produces inositol pyrophosphates from InsP6 |
| MINPP1 (human) | Multiple inositol polyphosphate phosphatase | Degrades inositol polyphosphates, opposing kinase activity |
| ITPK1 (Arabidopsis) | Inositol 1,3,4-trisphosphate 5/6-kinase | Plant homolog with 6-kinase activity |
| AtITPK4 (Arabidopsis) | Outlier ATP-grasp fold protein | Structural and functional studies of plant 6-kinases |
| Ins(1,4,5)P3 6-kinase (pea) | First biochemically characterized plant 6-kinase | Foundational enzyme for plant inositol phosphate research |
| IpmK (S. cerevisiae) | Inositol polyphosphate multikinase | Regulates Ins(1,4,5,6)P4 levels |
| Ins(1,3,4)P3 6-kinase (liver) | Liver enzyme acting on Ins(1,3,4)P3 | Demonstrates 6-kinase activity on multiple substrates |
| Ins(1,4,5)P3 6-kinase (yeast) | Purified enzyme with 6-kinase activity | Biochemical characterization of the activity |
How Is inositol-1,4,5-trisphosphate 6-kinase activity Regulated?
The activity of inositol-1,4,5-trisphosphate 6-kinase is regulated at multiple levels. Substrate availability of Ins(1,4,5)P3, generated by phospholipase C, directly controls flux through this branch. ATP levels and divalent cation concentrations modulate catalytic rate, as shown for the purified yeast and pea enzymes. In yeast, IpmK regulates Ins(1,4,5,6)P4 levels, and its expression is linked to arginine metabolism and stress signaling. Competing 3-kinase activity can divert Ins(1,4,5)P3 toward a different metabolic pathway, effectively reducing substrate for 6-kinase. In plants, ITPK4 is an outlier ATP-grasp fold protein whose activity may be regulated by structural features distinct from canonical kinases. Small-molecule inhibitors such as chiro-inositol tetrakisphosphate analogs can acutely block related kinase activities, providing pharmacological regulation. Isotopically labeled substrates enable precise measurement of flux through this activity under different cellular conditions.
inositol-1,4,5-trisphosphate 6-kinase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| IPMK (human) | Cancer cell proliferation and survival | CRISPR knockout in cancer cell lines |
| IPK2 (yeast) | Arginine metabolism and stress response | Yeast knockout and point-mutation models |
| ITPK4 (Arabidopsis) | Plant stress signaling and development | Arabidopsis knockout and overexpression lines |
| ITPK1 (human) | Inositol polyphosphate-related metabolic disorders | Knock-in of patient variants in HEK293 cells |
| Ins(1,4,5)P3 6-kinase (pea) | Plant inositol phosphate metabolism | Pea root enzyme assays and mutant screens |
Cancer and cell proliferation
Inositol polyphosphate kinases, including those with 6-kinase activity, have been implicated in cancer cell proliferation and survival. Altered levels of Ins(1,4,5,6)P4 and higher inositol polyphosphates can affect signaling pathways that control cell cycle progression and apoptosis. Inhibitors of related inositol polyphosphate kinases, such as chiro-inositol tetrakisphosphate derivatives, have shown biological activity in cancer models, suggesting that targeting GO:0000823 could be therapeutically relevant. The metabolic branch point between 3-kinase and 6-kinase activities may determine whether cells favor calcium signaling or inositol pyrophosphate production, with consequences for tumor growth.
Neurodegeneration and neuronal signaling
Inositol polyphosphate signaling is critical for neuronal function, and dysregulation of Ins(1,4,5)P3 metabolism has been linked to neurodegenerative conditions. Ins(1,4,5,6)P4 can modulate ion channels and calcium homeostasis, processes that are perturbed in neurodegeneration. The 6-kinase activity therefore represents a potential node for therapeutic intervention in diseases where phosphoinositide signaling is disrupted. However, direct evidence linking GO:0000823 to specific neurodegenerative diseases remains an active area of research.
Metabolic and stress-related disorders
In yeast, IpmK regulates Ins(1,4,5,6)P4 levels and influences arginine metabolism and stress responses, indicating a role in metabolic adaptation. In plants, ITPK4 contributes to inositol polyphosphate diversity, which is important for stress signaling and development. These findings suggest that 6-kinase activity may be relevant to metabolic disorders and stress-related pathologies in higher organisms. The use of 13C-labeled Ins(1,4,5)P3 enables metabolic tracing to quantify flux through this pathway in disease models.
From inositol-1,4,5-trisphosphate 6-kinase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of 6-kinase activity alter Ins(1,4,5,6)P4 levels? | CRISPR knockout of IPMK or IPK2 in human or yeast cells |
| Which catalytic residues are essential for 6-kinase activity? | Point mutation of predicted ATP-grasp fold residues in ITPK4 |
| Can a disease-associated variant affect 6-kinase activity? | Knock-in of patient variants into endogenous IPMK locus |
| Where is the enzyme localized in cells? | Tagged knock-in of IPMK with fluorescent protein |
| Does overexpression of 6-kinase change inositol polyphosphate profiles? | Overexpression of IPMK or ITPK4 in cell lines |
| Can small-molecule inhibitors block 6-kinase activity? | CRISPR knockout plus inhibitor treatment in cancer cells |
How to Study the inositol-1,4,5-trisphosphate 6-kinase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Kinase assay with radioactive ATP | Enzymatic conversion of Ins(1,4,5)P3 to Ins(1,4,5,6)P4 | Validation of purified enzyme or CRISPR mutants |
| HPLC separation of inositol phosphates | Levels of inositol polyphosphate isomers | Profiling cellular inositol phosphate pools |
| Mass spectrometry | Quantification of Ins(1,4,5,6)P4 and related metabolites | Metabolic tracing with 13C-labeled substrate |
| NMR spectroscopy | Structural identification of inositol phosphates | Characterization of reaction products |
| CRISPR knockout screening | Genes required for 6-kinase activity or product formation | Functional genomics of inositol polyphosphate pathway |
| Fluorescent tagging | Subcellular localization of the enzyme | Live-cell imaging of IPMK or ITPK4 |
| Site-directed mutagenesis | Catalytic residues essential for activity | Structure-function studies of ATP-grasp fold |
| Inhibitor profiling | Sensitivity of 6-kinase to small molecules | Drug discovery targeting inositol polyphosphate kinases |
Biochemical kinase assays
Direct measurement of GO:0000823 activity uses purified enzyme or cell lysates incubated with Ins(1,4,5)P3 and ATP, followed by separation of products by HPLC or mass spectrometry. The pea root enzyme was characterized using such assays, establishing the basic kinetic parameters. Yeast Ins(1,4,5)P3 6-kinase was purified and its properties defined using similar biochemical methods. These assays remain the gold standard for validating CRISPR-generated mutants.
Metabolic labeling and tracing
Semi-enzymatic synthesis of 13C-isotopically labeled Ins(1,4,5)P3 enables metabolic tracing of 6-kinase activity in living cells. Cells are incubated with labeled substrate, and downstream metabolites are quantified by NMR or mass spectrometry. This approach can reveal flux changes in CRISPR knockout or knock-in models. It is particularly useful for distinguishing between 3-kinase and 6-kinase branches.
Genetic screens and CRISPR libraries
CRISPR library screening can identify genes that modify 6-kinase activity or Ins(1,4,5,6)P4 levels. In yeast, deletion libraries have been used to map the inositol polyphosphate network, including IpmK. In Arabidopsis, T-DNA insertion lines for ITPK4 have been characterized to study plant inositol polyphosphate diversity. These screens can uncover novel regulators and disease-relevant pathways.
Structural and computational analysis
The ATP-grasp fold of ITPK4 and related kinases has been analyzed structurally to understand substrate binding and catalysis. Computational modeling of the active site can predict the effects of point mutations generated by CRISPR. Such analyses complement biochemical assays and help interpret disease variants.
How CRISPR Can Be Used to Study GO:0000823 inositol-1,4,5-trisphosphate 6-kinase activity
Knockout
CRISPR knockout of IPMK, IPK2, or ITPK4 eliminates 6-kinase activity, allowing researchers to measure the contribution of this enzyme to Ins(1,4,5,6)P4 production and downstream signaling. Knockout yeast strains show altered inositol polyphosphate profiles and stress responses. In human cells, IPMK knockout can reveal effects on cell proliferation and survival. These models are essential for establishing causality between GO:0000823 and cellular phenotypes.
Point Mutation
Point mutations in catalytic residues of the ATP-grasp fold can selectively abolish 6-kinase activity without affecting protein stability. CRISPR-mediated point mutation of ITPK4 or IPMK allows precise testing of structure-function relationships. Such models can distinguish between catalytic and scaffolding functions of the enzyme. They are also useful for validating disease-associated variants.
Knock-in
Knock-in of fluorescent tags or epitope tags into the endogenous IPMK locus enables real-time tracking of enzyme localization and interactions. Knock-in of patient-derived mutations can model disease-associated changes in 6-kinase activity. In plants, knock-in of ITPK4 variants can test their effects on inositol polyphosphate diversity. These models preserve endogenous regulatory context.
Overexpression
Overexpression of IPMK or ITPK4 increases 6-kinase activity and can elevate Ins(1,4,5,6)P4 levels. This approach is useful for gain-of-function studies and for producing sufficient enzyme for biochemical assays. Overexpression in cancer cells can test whether increased 6-kinase activity promotes proliferation. It also enables metabolic tracing with labeled substrates.
How EDITGENE Supports inositol-1,4,5-trisphosphate 6-kinase activity Research
Researchers studying inositol-1,4,5-trisphosphate 6-kinase activity-related genes often need to determine whether a candidate gene is causally involved in Ins(1,4,5,6)P4 production, cellular signaling, or disease phenotypes. EDITGENE provides CRISPR-based cell model services that enable precise genetic manipulation of IPMK, IPK2, ITPK4, and related genes.
Contact EDITGENE today to design your custom CRISPR model for inositol-1,4,5-trisphosphate 6-kinase activity research.
Frequently Asked Questions About inositol-1,4,5-trisphosphate 6-kinase activity
What is inositol-1,4,5-trisphosphate 6-kinase activity?
It is the enzymatic activity (GO:0000823) that phosphorylates Ins(1,4,5)P3 at the 6-position to produce Ins(1,4,5,6)P4, using ATP as the phosphate donor.
What genes are involved in inositol-1,4,5-trisphosphate 6-kinase activity?
Key genes include IPK2/ARG82 in yeast, ITPK4 in Arabidopsis, and IPMK in humans, all of which encode enzymes with 6-kinase activity.
What is the reaction catalyzed by GO:0000823?
The reaction is: 1D-myo-inositol 1,4,5-trisphosphate + ATP = 1D-myo-inositol 1,4,5,6-tetrakisphosphate + ADP + H+.
How is inositol-1,4,5-trisphosphate 6-kinase activity different from 3-kinase activity?
6-kinase phosphorylates the 6-position of Ins(1,4,5)P3, while 3-kinase phosphorylates the 3-position, generating different tetrakisphosphate isomers and initiating distinct metabolic branches.
Which diseases are linked to inositol-1,4,5-trisphosphate 6-kinase activity?
Altered activity has been implicated in cancer, neurodegeneration, and metabolic disorders, though direct causal links are still being investigated.
How can I study inositol-1,4,5-trisphosphate 6-kinase activity in the lab?
Biochemical kinase assays, metabolic labeling with 13C-Ins(1,4,5)P3, HPLC, mass spectrometry, and CRISPR knockout models are commonly used.
What is the role of IPMK in inositol polyphosphate metabolism?
IPMK (inositol polyphosphate multikinase) catalyzes 6-kinase activity and regulates Ins(1,4,5,6)P4 levels, influencing downstream inositol pyrophosphate synthesis.
Can CRISPR be used to study GO:0000823?
Yes, CRISPR knockout, point mutation, knock-in, and overexpression models enable precise dissection of 6-kinase function in cells and organisms.
What are the substrates and products of inositol-1,4,5-trisphosphate 6-kinase?
The substrate is Ins(1,4,5)P3 and ATP; the products are Ins(1,4,5,6)P4, ADP, and a proton.
Are there inhibitors of inositol-1,4,5-trisphosphate 6-kinase activity?
Synthetic chiro-inositol tetrakisphosphate analogs have been designed as inhibitors of related inositol polyphosphate kinases, providing chemical tools for studying this activity.
Conclusion
Inositol-1,4,5-trisphosphate 6-kinase activity (GO:0000823) is a conserved enzymatic function that converts Ins(1,4,5)P3 to Ins(1,4,5,6)P4, shaping the inositol polyphosphate signaling landscape. Its role at a metabolic branch point makes it a critical node for understanding cellular signaling in health and disease. Researchers can now leverage CRISPR-based knockout, point-mutation, knock-in, and overexpression models to dissect the causal contributions of IPMK, IPK2, ITPK4, and related genes. Combined with biochemical assays and metabolic tracing, these approaches will continue to reveal how GO:0000823 influences cancer, neurodegeneration, and metabolic disorders.
References
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- 6. 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
- 7. 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
- 8. Estevez F et al.. 1994. Inositol trisphosphate metabolism in Saccharomyces cerevisiae: identification, purification and properties of inositol 1,4,5-trisphosphate 6-kinase.. Biochem J 302 ( Pt 3)(Pt 3):709-16 PMID: 7945194
