GO:0047938 glucose-6-phosphate 1-epimerase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0047938 describes glucose-6-phosphate 1-epimerase activity, the catalysis of the interconversion of alpha-D-glucose 6-phosphate and beta-D-glucose 6-phosphate.
• This mutarotase activity supplies the correct anomeric form of glucose 6-phosphate for downstream metabolic enzymes.
• The enzyme is conserved across fungi, plants, and other eukaryotes, where it supports glycolysis, the Leloir pathway, and cell wall precursor supply.
• In the fungus Clonostachys chloroleuca, CrGlu6 contributes to development and biocontrol efficiency.
• In maize, ZmG6PE influences low-phosphorus stress responses and grain yield.
• CRISPR knockout, point-mutation, knock-in, and overexpression models enable causal testing of glucose-6-phosphate 1-epimerase function in diverse organisms.
Description
Glucose-6-phosphate 1-epimerase activity (GO:0047938) is a molecular function that catalyzes the reversible interconversion of the two anomeric forms of glucose 6-phosphate: alpha-D-glucose 6-phosphate and beta-D-glucose 6-phosphate. This reaction is a mutarotation step that does not consume ATP or change the chemical composition of the sugar phosphate; instead, it ensures that the correct anomer is available for enzymes that are stereospecific. The QuickGO definition states: Catalysis of the reaction: alpha-D-glucose 6-phosphate = beta-D-glucose 6-phosphate. Researchers study this activity because glucose 6-phosphate sits at the crossroads of glycolysis, the pentose phosphate pathway, glycogen metabolism, and cell wall biosynthesis, and the anomeric form can influence flux through these routes. In the filamentous fungus Clonostachys chloroleuca, the glucose-6-phosphate 1-epimerase CrGlu6 contributes to development and biocontrol efficiency, linking this seemingly simple mutarotation step to complex biological outcomes. In maize, ZmG6PE is involved in responses to low-phosphorus stress and regulation of grain yield, showing that the enzyme has agronomic relevance. In Aspergillus nidulans, L-arabinose induces D-galactose catabolism via the Leloir pathway, a pathway that depends on sugar phosphate interconversions including those mediated by mutarotases. The broader family of mutarotases, including sulfoquinovose mutarotase, has been characterized kinetically, providing mechanistic insight into how these enzymes accelerate anomer exchange. Together, these findings position GO:0047938 as a conserved and functionally significant activity in microbial, plant, and potentially human metabolic contexts.
glucose-6-phosphate 1-epimerase activity At A Glance
| GO ID | GO:0047938 |
|---|---|
| GO term | glucose-6-phosphate 1-epimerase activity |
| Ontology | molecular_function |
| Synonym | D-glucose-6-phosphate 1-epimerase activity; glucose-6 phosphate 1-epimerase activity |
| Definition | Catalysis of the reaction: alpha-D-glucose 6-phosphate = beta-D-glucose 6-phosphate |
| Major function | Interconversion of alpha- and beta-anomers of glucose 6-phosphate |
| Reaction type | Epimerization / mutarotation |
| Cofactors | None required |
| Subcellular context | Cytosol and possibly other compartments depending on organism |
| Representative genes | CrGlu6 in Clonostachys chloroleuca; ZmG6PE in maize; homologs in Aspergillus nidulans and other eukaryotes |
What Is GO:0047938?
Glucose-6-phosphate 1-epimerase activity is the catalytic activity that interconverts alpha-D-glucose 6-phosphate and beta-D-glucose 6-phosphate. It is classified as a molecular function in the Gene Ontology under GO:0047938. The reaction is an epimerization at the anomeric carbon, also known as mutarotation, and it does not require cofactors such as ATP or NAD+. The enzyme belongs to the mutarotase family, which includes other sugar phosphate mutarotases such as sulfoquinovose mutarotase. By equilibrating the alpha and beta anomers, the enzyme prepares glucose 6-phosphate for stereospecific downstream enzymes.
Why Is glucose-6-phosphate 1-epimerase activity Important in Cell Biology?
Glucose-6-phosphate 1-epimerase activity is important because it controls the anomeric form of a central metabolite, glucose 6-phosphate, which is a hub for glycolysis, the pentose phosphate pathway, glycogen synthesis, and cell wall precursor production. Without this mutarotation activity, stereospecific enzymes may encounter the wrong anomer and catalytic efficiency could be reduced. In fungi, the enzyme contributes to development and biocontrol efficiency, indicating roles beyond basic metabolism. In plants, it affects low-phosphorus stress responses and grain yield, linking it to crop performance. In Aspergillus nidulans, the Leloir pathway for D-galactose catabolism depends on sugar phosphate interconversions that include mutarotation steps. Thus, GO:0047938 is a conserved activity with metabolic, developmental, and agronomic significance.
• Supplies the correct anomer of glucose 6-phosphate for stereospecific enzymes in glycolysis and related pathways.
• Contributes to fungal development and biocontrol efficiency in Clonostachys chloroleuca.
• Influences low-phosphorus stress responses and grain yield in maize.
• Supports the Leloir pathway for D-galactose catabolism in Aspergillus nidulans.
• Represents a conserved mutarotase family activity with mechanistic parallels to sulfoquinovose mutarotase.
• Provides a target for CRISPR knockout and overexpression studies to test causal roles in metabolism and development.
• May affect metabolic flux distribution between glycolysis and the pentose phosphate pathway.
• Has potential agronomic relevance through effects on grain yield in maize.
• Can be studied using kinetic exchange spectroscopy as demonstrated for related mutarotases.
• Offers a model for understanding anomer-specific enzyme interactions in central carbon metabolism.
Molecular Mechanism of glucose-6-phosphate 1-epimerase activity
Substrate binding and anomer recognition
In simple terms: The enzyme grabs glucose 6-phosphate and recognizes which anomer it is holding.
Glucose-6-phosphate 1-epimerase binds glucose 6-phosphate and facilitates the opening of the sugar ring, allowing rotation around the anomeric carbon. The enzyme must accommodate both alpha- and beta-anomers because the reaction is reversible. Kinetic analysis of related mutarotases, such as sulfoquinovose mutarotase, has shown that substrate binding and release are fast steps that can be resolved by exchange spectroscopy. In Clonostachys chloroleuca, the CrGlu6 protein is annotated with this activity and contributes to development, implying that substrate recognition is linked to biological function.
Catalytic mechanism of anomer interconversion
In simple terms: The enzyme flips the sugar's anomeric configuration without using energy.
The catalytic mechanism involves general acid-base chemistry to open the sugar ring and allow rotation, followed by ring closure to yield the opposite anomer. This process does not require ATP or other cofactors, distinguishing it from kinases and dehydrogenases. The reaction reaches equilibrium between alpha- and beta-D-glucose 6-phosphate. Related mutarotases have been characterized using kinetic analysis at equilibrium by exchange spectroscopy, which revealed details of the catalytic cycle. The maize enzyme ZmG6PE is annotated with this activity and affects low-phosphorus stress responses, suggesting that catalytic efficiency may influence pathway flux.
Cofactors and metal requirements
In simple terms: No special helper molecules are needed for this reaction.
Glucose-6-phosphate 1-epimerase activity does not require cofactors such as NAD+ or metal ions, based on the defined reaction. This contrasts with many metabolic enzymes that depend on nucleotides or divalent cations. The absence of cofactor requirements simplifies kinetic studies and makes the enzyme suitable for in vitro assays. The sulfoquinovose mutarotase, a related enzyme, was characterized without invoking metal cofactors, supporting the notion that mutarotases operate through protein-based acid-base catalysis.
Regulation and integration with metabolic pathways
In simple terms: The enzyme's activity is tuned to the needs of the cell's sugar metabolism.
The activity of glucose-6-phosphate 1-epimerase is integrated with glycolysis, the pentose phosphate pathway, and cell wall biosynthesis, although direct allosteric regulation has not been extensively documented. In Aspergillus nidulans, L-arabinose induces D-galactose catabolism via the Leloir pathway, which involves sugar phosphate interconversions that may include mutarotation steps. In maize, ZmG6PE expression or activity is associated with low-phosphorus stress responses and grain yield, suggesting transcriptional or post-transcriptional regulation. The yeast RNase Z complex, Trz1, forms a stable heterohexamer with endonuclease Nuc1 and mutarotase, indicating that mutarotases can be part of larger protein assemblies with regulatory roles.
Key Genes Involved in GO:0047938 glucose-6-phosphate 1-epimerase activity
The following genes and proteins are experimentally linked to glucose-6-phosphate 1-epimerase activity or its biological roles.
| Gene | Major Role | Research Relevance |
|---|---|---|
| CrGlu6 | Glucose-6-phosphate 1-epimerase in Clonostachys chloroleuca | Contributes to development and biocontrol efficiency |
| ZmG6PE | Glucose-6-phosphate 1-epimerase in maize | Involved in low-phosphorus stress responses and grain yield |
| Aspergillus nidulans Leloir pathway genes | D-galactose catabolism via Leloir pathway | L-arabinose induces D-galactose catabolism, involving sugar phosphate interconversions |
| Sulfoquinovose mutarotase | Related mutarotase enzyme | Characterized by kinetic analysis at equilibrium by exchange spectroscopy |
| Trz1 | Long form RNase Z from yeast | Forms a stable heterohexamer with endonuclease Nuc1 and mutarotase |
| Nuc1 | Endonuclease in yeast | Partners with Trz1 and mutarotase in a heterohexamer |
| Yeast mutarotase | Mutarotase in yeast | Component of the Trz1-Nuc1 heterohexamer |
| Human homologs of mutarotases | Predicted glucose-6-phosphate 1-epimerase activity | Potential roles in metabolic regulation, inferred from conserved family |
| Plant G6PE homologs | Sugar phosphate interconversion | May affect stress responses and yield |
| Fungal G6PE homologs | Development and biocontrol | Demonstrated in Clonostachys chloroleuca |
| Bacterial mutarotases | Sugar anomer interconversion | Model enzymes for mechanistic studies |
| Sulfoquinovose mutarotase (SQ mutarotase) | Sulfosugar anomer interconversion | Kinetic model for mutarotation |
| Glucose-6-phosphatase | Removes excess substrate from brain | Related to glucose-6-phosphate metabolism |
| Brain glucose transporters | Cerebral glucose uptake | Two pools of glucose and role of glucose-6-phosphatase |
| Leloir pathway enzymes | Galactose catabolism | Induced by L-arabinose in Aspergillus nidulans |
| Glycolytic enzymes | Glucose 6-phosphate utilization | Depend on correct anomer for activity |
| Pentose phosphate pathway enzymes | Glucose 6-phosphate oxidation | May require specific anomer |
How Is glucose-6-phosphate 1-epimerase activity Regulated?
Regulation of glucose-6-phosphate 1-epimerase activity is not well characterized at the allosteric level, but its expression and biological impact are modulated by developmental and environmental cues. In Clonostachys chloroleuca, CrGlu6 contributes to development and biocontrol efficiency, suggesting that its expression is integrated with fungal life cycle programs. In maize, ZmG6PE is involved in responses to low-phosphorus stress and regulation of grain yield, indicating that its activity or expression responds to nutrient status. In Aspergillus nidulans, L-arabinose induces D-galactose catabolism via the Leloir pathway, which may indirectly regulate mutarotase demand. The yeast Trz1-Nuc1-mutarotase heterohexamer suggests that mutarotase can be part of a regulated complex. Additionally, cerebral glucose metabolism studies have highlighted the role of glucose-6-phosphatase in removing excess substrate from brain, which indirectly affects glucose 6-phosphate pools available to epimerases.
glucose-6-phosphate 1-epimerase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| CrGlu6 | Fungal development and biocontrol efficiency | Clonostachys chloroleuca knockout and overexpression strains |
| ZmG6PE | Low-phosphorus stress and grain yield in maize | Maize knockout and overexpression lines |
| Aspergillus nidulans Leloir pathway genes | D-galactose catabolism | Aspergillus nidulans mutants and induction studies |
| Glucose-6-phosphatase | Cerebral glucose homeostasis | Brain metabolic studies and knockout models |
| Yeast Trz1/Nuc1/mutarotase | RNase Z complex function | Yeast heterohexamer assembly assays |
Metabolic disorders and glucose-6-phosphate imbalance
Glucose-6-phosphate 1-epimerase activity influences the anomeric form of glucose 6-phosphate, a central metabolite in glycolysis and the pentose phosphate pathway. Disruption of this activity could alter flux through these pathways, potentially contributing to metabolic disorders. In brain, glucose-6-phosphatase removes excess substrate from the glucose 6-phosphate pool, and perturbations in this balance may affect neuronal metabolism. However, direct evidence linking GO:0047938 to human metabolic disease is currently limited, and most insights come from model organisms.
Fungal pathogenesis and biocontrol
In the fungus Clonostachys chloroleuca, the glucose-6-phosphate 1-epimerase CrGlu6 contributes to development and biocontrol efficiency. This suggests that targeting this activity could affect fungal fitness and interactions with plant hosts or pathogens. While not a human disease, this finding has implications for agricultural biocontrol and for understanding fungal metabolic adaptations.
Plant stress responses and crop yield
In maize, ZmG6PE is involved in responses to low-phosphorus stress and regulation of grain yield. This links glucose-6-phosphate 1-epimerase activity to plant nutrition and productivity. Alterations in this activity could affect crop performance under nutrient limitation, making it a potential target for agricultural biotechnology.
Neurological implications of glucose-6-phosphate metabolism
Cerebral glucose metabolism involves two pools of glucose and the action of glucose-6-phosphatase in removing excess substrate from brain. Although glucose-6-phosphate 1-epimerase is not directly implicated in neurological disease in the cited literature, its role in maintaining glucose 6-phosphate anomer balance could influence neuronal energy metabolism. Further research is needed to establish any direct link.
From glucose-6-phosphate 1-epimerase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of glucose-6-phosphate 1-epimerase affect fungal development? | CRISPR knockout of CrGlu6 in Clonostachys chloroleuca |
| Does overexpression of ZmG6PE improve low-phosphorus tolerance? | Overexpression of ZmG6PE in maize |
| Does a point mutation in the catalytic site abolish mutarotase activity? | Point-mutation knock-in in a model enzyme such as sulfoquinovose mutarotase |
| Does tagging the enzyme affect its interaction with the Trz1-Nuc1 complex? | Tagged knock-in of mutarotase in yeast |
| Does knockout of glucose-6-phosphate 1-epimerase alter glycolysis flux? | CRISPR knockout in a model cell line followed by metabolomics |
| Can mutarotase activity be measured in real time? | Kinetic exchange spectroscopy on purified enzyme |
How to Study the glucose-6-phosphate 1-epimerase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Kinetic exchange spectroscopy | Rate of anomer interconversion | Mechanistic characterization of mutarotases |
| CRISPR knockout | Loss-of-function phenotypes | Testing gene function in fungi and plants |
| Overexpression | Gain-of-function phenotypes | Assessing effects on stress tolerance and yield |
| Metabolomics | Glucose 6-phosphate levels and anomer ratios | Pathway flux analysis |
| Co-immunoprecipitation | Protein-protein interactions | Identifying mutarotase complexes |
| Enzyme assays | Catalytic activity | Measuring glucose-6-phosphate 1-epimerase activity in vitro |
| Transcriptomics | Gene expression changes | Linking activity to developmental or stress programs |
| Structural biology | Three-dimensional structure | Understanding catalytic mechanism |
Kinetic analysis by exchange spectroscopy
Kinetic analysis at equilibrium by exchange spectroscopy has been used to characterize sulfoquinovose mutarotase, a related enzyme, providing a template for studying glucose-6-phosphate 1-epimerase activity. This method measures the rate of anomer interconversion and can resolve individual catalytic steps. Applying this approach to GO:0047938 enzymes would yield detailed mechanistic insights.
Genetic knockout and overexpression in fungi and plants
CRISPR knockout and overexpression of CrGlu6 in Clonostachys chloroleuca and ZmG6PE in maize have been used to link the activity to development, biocontrol, stress responses, and yield. These genetic approaches are essential for establishing causal roles of glucose-6-phosphate 1-epimerase in whole organisms.
Metabolomics and flux analysis
Metabolomic profiling can measure glucose 6-phosphate levels and anomer ratios, while flux analysis can assess pathway utilization. Such methods help determine how changes in glucose-6-phosphate 1-epimerase activity affect central carbon metabolism. In brain, glucose-6-phosphatase activity influences glucose 6-phosphate pools, highlighting the importance of measuring these metabolites.
Protein interaction studies
The yeast Trz1-Nuc1-mutarotase heterohexamer demonstrates that mutarotases can participate in protein complexes. Co-immunoprecipitation, crosslinking, and structural biology can reveal whether glucose-6-phosphate 1-epimerase interacts with other proteins. Such studies may uncover regulatory roles beyond catalysis.
How CRISPR Can Be Used to Study GO:0047938 glucose-6-phosphate 1-epimerase activity
Knockout
CRISPR knockout of glucose-6-phosphate 1-epimerase genes such as CrGlu6 in Clonostachys chloroleuca or ZmG6PE in maize can reveal loss-of-function phenotypes in development, biocontrol, stress responses, and yield. Knockout models are essential for determining whether the activity is required for specific biological processes.
Point Mutation
Point mutations in the catalytic residues of glucose-6-phosphate 1-epimerase can be introduced using CRISPR base editing or homology-directed repair to test which amino acids are essential for mutarotation. Such models help distinguish catalytic activity from potential structural roles.
Knock-in
Knock-in of epitope tags or fluorescent proteins at the endogenous locus allows visualization and interaction studies of glucose-6-phosphate 1-epimerase in its native context. Tagged knock-in can also be used to study complex formation, as seen with the yeast Trz1-Nuc1-mutarotase heterohexamer.
Overexpression
CRISPR activation or transgenic overexpression of glucose-6-phosphate 1-epimerase genes can test gain-of-function effects on metabolism, stress tolerance, and yield. Overexpression of ZmG6PE in maize has been linked to low-phosphorus stress responses and grain yield regulation.
How EDITGENE Supports glucose-6-phosphate 1-epimerase activity Research
Researchers studying glucose-6-phosphate 1-epimerase activity-related genes often need to determine whether a candidate gene is causally involved in metabolic, developmental, or stress-related phenotypes. EDITGENE provides CRISPR-based cell and organism models to enable such causal testing with high precision.
Contact EDITGENE today to design your custom CRISPR model for glucose-6-phosphate 1-epimerase activity research.
Frequently Asked Questions About glucose-6-phosphate 1-epimerase activity
What is glucose-6-phosphate 1-epimerase activity?
It is the catalytic activity that interconverts alpha-D-glucose 6-phosphate and beta-D-glucose 6-phosphate, defined as GO:0047938.
What genes are involved in glucose-6-phosphate 1-epimerase activity?
Genes include CrGlu6 in Clonostachys chloroleuca, ZmG6PE in maize, and homologs in Aspergillus nidulans and other eukaryotes.
What is the GO ID for glucose-6-phosphate 1-epimerase activity?
The GO ID is GO:0047938.
What reaction does glucose-6-phosphate 1-epimerase catalyze?
It catalyzes the reversible interconversion of alpha-D-glucose 6-phosphate and beta-D-glucose 6-phosphate.
Why is glucose-6-phosphate 1-epimerase important in fungi?
In Clonostachys chloroleuca, CrGlu6 contributes to development and biocontrol efficiency.
How does glucose-6-phosphate 1-epimerase affect plants?
In maize, ZmG6PE is involved in low-phosphorus stress responses and regulation of grain yield.
Is glucose-6-phosphate 1-epimerase related to the Leloir pathway?
Yes, in Aspergillus nidulans, L-arabinose induces D-galactose catabolism via the Leloir pathway, which involves sugar phosphate interconversions.
What methods are used to study glucose-6-phosphate 1-epimerase activity?
Methods include kinetic exchange spectroscopy, CRISPR knockout, overexpression, metabolomics, and protein interaction studies.
Can CRISPR be used to study glucose-6-phosphate 1-epimerase?
Yes, CRISPR knockout, point mutation, knock-in, and overexpression are all applicable to study this activity.
What diseases are linked to glucose-6-phosphate 1-epimerase activity?
Direct links to human disease are limited; however, it affects fungal biocontrol, plant stress responses, and cerebral glucose metabolism indirectly.
Conclusion
Glucose-6-phosphate 1-epimerase activity (GO:0047938) is a conserved molecular function that interconverts the alpha- and beta-anomers of glucose 6-phosphate, supporting glycolysis, the Leloir pathway, and cell wall metabolism. Experimental evidence from fungi and plants shows that this activity contributes to development, biocontrol efficiency, stress responses, and grain yield. Related mutarotases have been characterized kinetically, providing mechanistic insights. CRISPR-based models are powerful tools for dissecting the causal roles of this activity in diverse organisms. Future research may uncover additional regulatory and disease-relevant functions of glucose-6-phosphate 1-epimerase.
References
- 1. Lv B et al.. 2023. Glucose-6-phosphate 1-Epimerase CrGlu6 Contributes to Development and Biocontrol Efficiency in Clonostachys chloroleuca.. J Fungi (Basel) 9(7) PMID: 37504752
- 2. Németh Z et al.. 2019. l-Arabinose induces d-galactose catabolism via the Leloir pathway in Aspergillus nidulans.. Fungal Genet Biol 123:53-59 PMID: 30496805
- 3. Zhang H et al.. 2023. Functional analysis of ZmG6PE reveals its role in responses to low-phosphorus stress and regulation of grain yield in maize.. Front Plant Sci 14:1286699 PMID: 38023907
- 4. Abayakoon P et al.. 2018. Discovery and characterization of a sulfoquinovose mutarotase using kinetic analysis at equilibrium by exchange spectroscopy.. Biochem J 475(7):1371-1383 PMID: 29535276
- 5. Sacks W et al.. 1985. Evidence for the cerebral uptake in vivo from two pools of glucose and the role of glucose-6-phosphatase in removing excess substrate from brain.. Neurochem Res 10(2):201-27 PMID: 2986020
- 6. Ma M et al.. 2017. Trz1, the long form RNase Z from yeast, forms a stable heterohexamer with endonuclease Nuc1 and mutarotase.. Biochem J 474(21):3599-3613 PMID: 28899942
