GO:0004512 inositol-3-phosphate synthase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0004512 (inositol-3-phosphate synthase activity) catalyzes the NAD-dependent cyclization of D-glucose 6-phosphate to 1D-myo-inositol 3-phosphate, the committed step in de novo inositol biosynthesis.
• The enzyme is conserved from yeast to humans; the human enzyme is functional in yeast, demonstrating evolutionary conservation of the catalytic mechanism.
• MIPS is regulated by phosphorylation, which modulates its activity and stability, providing a novel regulatory mechanism for inositol biosynthesis.
• Valproate, a mood stabilizer, reduces MIPS expression, linking inositol synthesis to neuropsychiatric disorders and drug response.
• Multiple isoforms exist, including a 16-kDa gamma(c) isoform with distinct expression patterns and putative roles.
• In plants and insects, MIPS overexpression elevates inositol levels and enhances abiotic stress tolerance, highlighting its biotechnological potential.
Description
Inositol-3-phosphate synthase (MIPS) is the enzyme responsible for the first and rate-limiting step in the de novo biosynthesis of myo-inositol, a crucial metabolite involved in diverse cellular processes including signal transduction, osmoprotection, and lipid synthesis. The enzyme catalyzes the conversion of D-glucose 6-phosphate to 1D-myo-inositol 3-phosphate in an NAD-dependent manner, a unique cyclization reaction that forms the inositol ring. This activity is encoded by the GO term GO:0004512 and is conserved across eukaryotes, from yeast to humans. Researchers study MIPS because myo-inositol and its derivatives are essential for cell signaling, membrane biogenesis, and stress responses, and dysregulation of inositol metabolism has been implicated in diseases such as bipolar disorder, diabetes, and cancer. Understanding the molecular mechanism, regulation, and physiological roles of MIPS is therefore of broad biomedical importance.
inositol-3-phosphate synthase activity At A Glance
| GO ID | GO:0004512 |
|---|---|
| GO term | inositol-3-phosphate synthase activity |
| Ontology | molecular_function |
| Synonym | D-glucose 6-phosphate cycloaldolase activity; glucose 6-phosphate cyclase activity; inositol 1-phosphate synthetase activity; 1L-myo-inositol-1-phosphate lyase (isomerizing) |
| Major function | Catalyzes the NAD-dependent cyclization of D-glucose 6-phosphate to 1D-myo-inositol 3-phosphate, the committed step in de novo inositol biosynthesis |
| Reaction | D-glucose 6-phosphate = 1D-myo-inositol 3-phosphate |
| Cofactor | NAD |
| Pathway | Inositol phosphate metabolism; phosphatidylinositol signaling system |
| Conservation | Present in bacteria, yeast, plants, and animals; human enzyme is functional in yeast |
What Is GO:0004512?
GO:0004512 (inositol-3-phosphate synthase activity) is a molecular function defined as the catalysis of the reaction: D-glucose 6-phosphate = 1D-myo-inositol 3-phosphate. This reaction requires NAD, which dehydrogenates the CHOH group to CO at C-5 of glucose 6-phosphate, making C-6 into an active methylene that can condense with the aldehyde at C-1. Finally, the enzyme-bound NADH reconverts C-5 into the CHOH form. The term is also known by synonyms such as D-glucose 6-phosphate cycloaldolase activity, glucose 6-phosphate cyclase activity, and inositol 1-phosphate synthetase activity.
Why Is inositol-3-phosphate synthase activity Important in Cell Biology?
GO:0004512 is critical because it governs the production of myo-inositol, a precursor for phosphatidylinositol and inositol phosphates that regulate membrane trafficking, signal transduction, and stress responses. Dysregulation of MIPS has been linked to bipolar disorder, as valproate reduces its expression, and to diabetes and cancer through altered inositol metabolism. In plants and insects, MIPS activity is essential for abiotic stress tolerance and development. Thus, understanding this enzyme provides insights into fundamental cell biology and potential therapeutic targets.
• Rate-limiting step in de novo inositol biosynthesis, essential for all eukaryotes.
• Produces myo-inositol, a precursor for phosphatidylinositol and inositol phosphates involved in signal transduction.
• Regulated by phosphorylation, linking cellular signaling to inositol production.
• Target of valproate, a mood stabilizer, implicating it in bipolar disorder.
• Overexpression in plants elevates inositol and enhances stress tolerance.
• Insect MIPS is involved in abiotic stress responses.
• Multiple isoforms with distinct expression patterns suggest specialized roles.
• Conserved mechanism allows use of yeast as a model for human enzyme studies.
• Phosphatidic acid regulates INO1 expression, connecting lipid signaling to inositol synthesis.
• Potential target for metabolic engineering and drug development.
Molecular Mechanism of inositol-3-phosphate synthase activity
Substrate Binding and NAD-Dependent Dehydrogenation
In simple terms: The enzyme grabs glucose 6-phosphate and uses NAD to remove hydrogens, setting up the ring closure.
MIPS binds D-glucose 6-phosphate and NAD, catalyzing the dehydrogenation of the CHOH group at C-5 to a carbonyl (CO), which activates C-6 as a methylene. This step is essential for the subsequent cyclization and is conserved across species.
Cyclization to Form the Inositol Ring
In simple terms: The activated molecule folds into a ring, creating inositol 3-phosphate.
The active methylene at C-6 condenses with the aldehyde at C-1, forming the inositol ring and yielding 1D-myo-inositol 3-phosphate. This intramolecular aldol condensation is the key cyclization step unique to MIPS.
NADH Reoxidation and Product Release
In simple terms: The enzyme recycles NADH back to NAD and releases the product.
The enzyme-bound NADH is reoxidized to NAD, possibly by an external electron acceptor, and the product 1D-myo-inositol 3-phosphate is released. The exact mechanism of NADH reoxidation may vary among organisms but is essential for catalytic turnover.
Regulation by Phosphorylation
In simple terms: Adding phosphate groups to the enzyme can turn its activity up or down.
MIPS is a phosphoprotein; phosphorylation regulates its activity and stability. This post-translational modification provides a rapid mechanism to adjust inositol synthesis in response to cellular signals.
Isoforms and Alternative Splicing
In simple terms: Different versions of the enzyme exist, possibly with specialized roles.
Multiple MIPS isoforms, including a 16-kDa gamma(c) isoform, have been identified with distinct expression patterns, suggesting tissue-specific or developmental roles. These isoforms may differ in regulation or subcellular localization.
Key Genes Involved in GO:0004512 inositol-3-phosphate synthase activity
The following genes and proteins are central to inositol-3-phosphate synthase activity and its regulation across model organisms.
| Gene | Major Role | Research Relevance |
|---|---|---|
| INO1 (S. cerevisiae) | Encodes MIPS; catalyzes de novo inositol synthesis | Model for studying regulation by phosphatidic acid and lipid signaling |
| ISYNA1 (human) | Encodes human MIPS; functional in yeast | Studied for human inositol metabolism and disease links |
| MIPS1 (Arabidopsis) | Encodes MIPS; overexpression elevates inositol | Used to enhance stress tolerance in plants |
| AccIPS1-B (Apis cerana cerana) | Insect MIPS involved in abiotic stress response | Model for stress adaptation in insects |
| MIPS (rat brain) | Phosphoprotein form of MIPS | Studied for phosphorylation-mediated regulation |
| MIPS (various) | Phosphorylation target | Regulation by phosphorylation modulates activity |
| MIPS gamma(c) isoform | 16-kDa isoform with distinct expression | Potential specialized functions in specific tissues |
| OPI1 (yeast) | Repressor of INO1 transcription | Regulates inositol synthesis in response to inositol levels |
| PA species 34:1 | Phosphatidic acid that mediates INO1 expression | Links lipid signaling to inositol synthesis |
| Valproate target | Reduces MIPS expression | Implicates MIPS in bipolar disorder treatment |
| Human ISYNA1 | Functional in yeast | Demonstrates conservation of catalytic mechanism |
| Plant MIPS | Overexpression increases inositol | Biotechnological applications for stress tolerance |
| Insect MIPS | Stress-responsive | Potential target for insect stress studies |
| Rat MIPS | Phosphoprotein | Model for post-translational regulation |
| Yeast INO1 | Regulated by phosphatidic acid | Model for lipid-mediated regulation |
| MIPS isoforms | Multiple forms | Isoform-specific functions |
| MIPS in disease | Linked to bipolar disorder | Therapeutic target |
How Is inositol-3-phosphate synthase activity Regulated?
MIPS activity is regulated at multiple levels. Phosphorylation of the enzyme modulates its activity and stability, providing a rapid post-translational mechanism. In yeast, phosphatidic acid species 34:1 mediates the expression of INO1, linking lipid signaling to inositol synthesis. Additionally, valproate reduces MIPS expression, suggesting pharmacological regulation. These regulatory mechanisms ensure that inositol production is tightly coupled to cellular needs and environmental cues.
inositol-3-phosphate synthase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| ISYNA1 (human) | Bipolar disorder; valproate response | Knockout or knockdown in neuronal cell lines; overexpression |
| MIPS (rat) | Phosphorylation in brain | Point mutations at phosphorylation sites |
| INO1 (yeast) | Lipid signaling and inositol regulation | Knockout and knock-in of INO1; phosphatidic acid treatment |
| MIPS1 (Arabidopsis) | Abiotic stress tolerance | Overexpression lines for stress assays |
| AccIPS1-B (insect) | Abiotic stress response | Knockdown or overexpression in insect cells |
Bipolar Disorder and Mood Stabilizers
Valproate, a mood stabilizer used in bipolar disorder, reduces the expression of myo-inositol-3-phosphate synthase, implicating MIPS in the therapeutic mechanism and in the pathophysiology of mood disorders. This suggests that inositol depletion may contribute to valproate's effects.
Metabolic Disorders and Cancer
Altered inositol metabolism has been linked to diabetes and cancer, where inositol phosphates play roles in cell signaling and growth control. MIPS phosphorylation may influence these pathways, making it a potential target for metabolic and oncological research.
Stress Response and Neuroprotection
In plants and insects, MIPS is involved in abiotic stress responses, and overexpression enhances stress tolerance. In animals, myo-inositol serves as an osmolyte and neuroprotectant, suggesting that MIPS regulation could impact neurological health.
From inositol-3-phosphate synthase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does MIPS knockout affect inositol levels and cell growth? | CRISPR knockout in human cell lines (e.g., HEK293) |
| How does phosphorylation regulate MIPS activity? | Point mutations at phosphorylation sites in MIPS |
| Can human MIPS rescue yeast inositol auxotrophy? | Knock-in of human ISYNA1 into yeast ino1 mutant |
| What is the effect of MIPS overexpression on stress tolerance? | Overexpression in Arabidopsis or insect cells |
| How does valproate affect MIPS expression? | Knockdown or overexpression followed by valproate treatment |
| What are the roles of MIPS isoforms? | Isoform-specific knockout or tagged knock-in |
How to Study the inositol-3-phosphate synthase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Enzymatic assay with NADH detection | MIPS catalytic activity | Kinetic studies of wild-type and mutants |
| Phospho-specific Western blot | Phosphorylation status of MIPS | Regulation by kinases/phosphatases |
| RNA-seq | MIPS mRNA expression | Response to valproate or stress |
| Mass spectrometry | Inositol and phosphatidylinositol levels | Metabolic impact of MIPS manipulation |
| CRISPR knockout | Loss-of-function phenotype | Essentiality and pathway analysis |
| Overexpression | Gain-of-function phenotype | Stress tolerance and inositol production |
| Site-directed mutagenesis | Specific residue function | Phosphorylation site mapping |
| Yeast complementation | Functional conservation | Testing human MIPS in yeast |
Enzymatic Activity Assays
MIPS activity can be measured using radiolabeled glucose 6-phosphate or by coupling to NADH production. These assays are essential to confirm the catalytic function of wild-type and mutant enzymes.
Phosphorylation Analysis
Phosphorylation of MIPS can be detected by immunoprecipitation followed by mass spectrometry or phospho-specific antibodies. This reveals regulatory sites and their impact on activity.
Gene Expression Profiling
RNA-seq or qPCR can quantify MIPS mRNA levels under various conditions, such as valproate treatment or stress, to understand transcriptional regulation.
Metabolic Profiling
Measuring inositol and its derivatives by HPLC or mass spectrometry provides a readout of MIPS activity in cells and tissues.
How CRISPR Can Be Used to Study GO:0004512 inositol-3-phosphate synthase activity
Knockout
CRISPR knockout of MIPS genes (e.g., ISYNA1 in human cells or INO1 in yeast) can abolish inositol synthesis, leading to inositol auxotrophy and growth defects. Such models are valuable to study the essentiality of MIPS and to identify compensatory pathways.
Point Mutation
Introducing point mutations at catalytic residues or phosphorylation sites (e.g., serine to alanine) allows precise dissection of MIPS regulation and mechanism. These models help determine the role of specific amino acids in catalysis or post-translational modification.
Knock-in
Knock-in of tagged MIPS (e.g., GFP or FLAG) enables visualization and purification of the enzyme for interaction studies. Additionally, knock-in of human ISYNA1 into yeast can test functional conservation.
Overexpression
CRISPR activation or cDNA overexpression of MIPS increases inositol production, which can enhance stress tolerance in plants or insects. Overexpression models are also used to study the effects of elevated inositol on cell signaling.
How EDITGENE Supports inositol-3-phosphate synthase activity Research
Researchers studying inositol-3-phosphate synthase activity-related genes often need to determine whether a candidate gene is causally involved in inositol metabolism, stress responses, or disease. EDITGENE provides comprehensive CRISPR-based services to create precise cellular models for such investigations.
Contact EDITGENE today to design your custom CRISPR model for inositol-3-phosphate synthase activity research.
Related Products
| Product name | Cat.No. | Species | Gene ID | |
|---|---|---|---|---|
| ISYNA1 Knockout HEK293 Cell Line | EDJ-KQ3299 | Human | 51477 | Details Get a Quote |
| ISYNA1 Knockout HCT 116 Cell Line | EDJ-KQ23494 | Human | 51477 | Details Get a Quote |
| ISYNA1 Knockout A-549 Cell Line | EDJ-KQ24880 | Human | 51477 | Details Get a Quote |
| ISYNA1 Knockout HeLa Cell Line | EDJ-KQ24882 | Human | 51477 | Details Get a Quote |
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Frequently Asked Questions About inositol-3-phosphate synthase activity
What is inositol-3-phosphate synthase activity?
It is the enzymatic activity (GO:0004512) that converts D-glucose 6-phosphate to 1D-myo-inositol 3-phosphate, the first step in de novo inositol synthesis.
What genes are involved in inositol-3-phosphate synthase activity?
Key genes include INO1 in yeast, ISYNA1 in humans, MIPS1 in Arabidopsis, and AccIPS1-B in insects.
How is inositol-3-phosphate synthase regulated?
It is regulated by phosphorylation and by lipid signaling molecules such as phosphatidic acid, and its expression is reduced by valproate.
What diseases are associated with inositol-3-phosphate synthase?
Bipolar disorder, diabetes, and cancer have been linked to altered MIPS activity or expression.
Can human inositol-3-phosphate synthase function in yeast?
Yes, human ISYNA1 can complement yeast ino1 mutants, demonstrating functional conservation.
What are the isoforms of inositol-3-phosphate synthase?
Multiple isoforms exist, including a 16-kDa gamma(c) isoform with distinct expression patterns.
How can I study inositol-3-phosphate synthase activity?
Use enzymatic assays, phosphorylation analysis, RNA-seq, and CRISPR knockout or overexpression models.
What is the reaction catalyzed by inositol-3-phosphate synthase?
D-glucose 6-phosphate = 1D-myo-inositol 3-phosphate, requiring NAD as a cofactor.
Why is inositol-3-phosphate synthase important for stress tolerance?
Overexpression in plants and insects increases inositol levels and enhances tolerance to abiotic stress.
How does valproate affect inositol-3-phosphate synthase?
Valproate reduces the expression of MIPS, which may contribute to its therapeutic effects in bipolar disorder.
Conclusion
Inositol-3-phosphate synthase activity (GO:0004512) is a fundamental enzymatic function that initiates de novo inositol biosynthesis in all eukaryotes. Its regulation by phosphorylation and lipid signaling, and its links to bipolar disorder, metabolic diseases, and stress responses, make it a compelling target for biomedical research. CRISPR-based models offer powerful tools to dissect its mechanism and therapeutic potential.
References
- 1. Case KC et al.. 2023. Valproate regulates inositol synthesis by reducing expression of myo-inositol-3-phosphate synthase.. Sci Rep 13(1):14844 PMID: 37684289
- 2. Parthasarathy RN et al.. 2013. Rat brain myo-inositol 3-phosphate synthase is a phosphoprotein.. Mol Cell Biochem 378(1-2):83-9 PMID: 23504145
- 3. Deranieh RM et al.. 2013. Phosphorylation regulates myo-inositol-3-phosphate synthase: a novel regulatory mechanism of inositol biosynthesis.. J Biol Chem 288(37):26822-33 PMID: 23902760
- 4. Ni Y et al.. 2019. Identification of an inositol-3-phosphate synthase 1-B gene (AccIPS1-B) from Apis cerana cerana and its role in abiotic stress.. Cell Stress Chaperones 24(6):1101-1113 PMID: 31512154
- 5. Seelan RS et al.. 2009. Identification of myo-inositol-3-phosphate synthase isoforms: characterization, expression, and putative role of a 16-kDa gamma(c) isoform.. J Biol Chem 284(14):9443-57 PMID: 19188364
- 6. Ju S et al.. 2004. Human 1-D-myo-inositol-3-phosphate synthase is functional in yeast.. J Biol Chem 279(21):21759-65 PMID: 15024000
- 7. Gaspar ML et al.. 2022. Phosphatidic acid species 34:1 mediates expression of the myo-inositol 3-phosphate synthase gene INO1 for lipid synthesis in yeast.. J Biol Chem 298(7):102148 PMID: 35716778
- 8. Smart CC et al.. 1997. Overexpression of D-myo-inositol-3-phosphate synthase leads to elevated levels of inositol in Arabidopsis.. Plant Mol Biol 33(5):811-20 PMID: 9106505
