GO:0004360 L-glutamine:D-fructose-6-phosphate transaminase (isomerizing) activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0004360 describes the enzyme activity that converts D-fructose 6-phosphate and L-glutamine into D-glucosamine 6-phosphate and L-glutamate, the first committed step of the hexosamine biosynthetic pathway.
• The enzyme is widely known as glucosamine-6-phosphate synthase (GlcN6P synthase) or glutamine:fructose-6-phosphate amidotransferase (GFAT) and is conserved from bacteria to humans [1,2].
• In Saccharomyces cerevisiae, overexpression of the corresponding L-glutamine:D-fructose-6-phosphate amidotransferase confers resistance to methylmercury, linking the activity to stress protection.
• The enzyme shows tissue- and sex-specific regulation, as demonstrated by sex differences in mouse submandibular gland activity.
• Recombinant human GFAT1 can be expressed and purified as an active His-tagged protein, enabling biochemical and structural studies.
• The yeast gene is transcriptionally regulated by pheromone signaling, indicating that GO:0004360 is integrated into developmental and stress-response programs.
Description
GO:0004360, L-glutamine:D-fructose-6-phosphate transaminase (isomerizing) activity, is a molecular function that catalyzes the reaction D-fructose 6-phosphate + L-glutamine = D-glucosamine 6-phosphate + L-glutamate. This reaction is the first and rate-limiting step of the hexosamine biosynthetic pathway, which produces UDP-N-acetylglucosamine and other amino sugars used in protein glycosylation and cell-wall biosynthesis. The enzyme responsible is commonly called glucosamine-6-phosphate synthase (GlcN6P synthase) or glutamine:fructose-6-phosphate amidotransferase (GFAT) [1,2]. Because the reaction commits fructose 6-phosphate to amino sugar metabolism, its regulation influences glycosylation, signaling, and stress responses in organisms ranging from bacteria to mammals [1,3]. Researchers study GO:0004360 to understand metabolic flux into the hexosamine pathway, to characterize enzyme kinetics and inhibition, and to explore its roles in development, immunity, and disease [1,2,5]. The activity has been purified from rat liver and from the extreme thermophile Thermus thermophilus, showing that the catalytic mechanism is conserved across diverse species [2,7]. In yeast, the gene encoding this activity is regulated by pheromone signaling, and its overexpression protects cells from methylmercury toxicity [3,6]. In mammals, the enzyme is expressed in a tissue-specific manner, with sex differences observed in the mouse submandibular gland. Recombinant human GFAT1 has been produced as an active His-tagged protein, facilitating detailed biochemical analysis. Anti-inflammatory agents can also affect the activity, suggesting pharmacological relevance. Together, these studies establish GO:0004360 as a central node in amino sugar metabolism with broad biological and biomedical significance [1,2,3,4,5,6,7,8].
L-glutamine:D-fructose-6-phosphate transaminase (isomerizing) activity At A Glance
| GO ID | GO:0004360 |
|---|---|
| GO term | L-glutamine:D-fructose-6-phosphate transaminase (isomerizing) activity |
| Ontology | molecular_function |
| Synonym | GlcN6P synthase activity; glucosamine 6-phosphate synthase activity; glutamine-fructose-6-phosphate transaminase (isomerizing) activity; hexosephosphate aminotransferase activity |
| Major function | Catalyzes the first committed step of the hexosamine biosynthetic pathway, converting fructose 6-phosphate and glutamine to glucosamine 6-phosphate and glutamate |
| Reaction | D-fructose 6-phosphate + L-glutamine = D-glucosamine 6-phosphate + L-glutamate |
| Organisms | Conserved from bacteria and yeast to mammals, including Thermus thermophilus, Saccharomyces cerevisiae, rat, mouse, and human [1,2,3,4,5,6,7] |
| Substrates | D-fructose 6-phosphate and L-glutamine |
| Products | D-glucosamine 6-phosphate and L-glutamate |
What Is GO:0004360?
GO:0004360 is defined as the catalysis of the reaction D-fructose 6-phosphate + L-glutamine = D-glucosamine 6-phosphate + L-glutamate. In other words, it is an enzyme activity that transfers the amino group from L-glutamine to D-fructose 6-phosphate, producing D-glucosamine 6-phosphate and L-glutamate. This activity is also known as glucosamine-6-phosphate synthase, glutamine:fructose-6-phosphate amidotransferase, or hexosephosphate aminotransferase.
Why Is L-glutamine:D-fructose-6-phosphate transaminase (isomerizing) activity Important in Cell Biology?
GO:0004360 is important because it controls the entry of glucose and glutamine metabolites into the hexosamine biosynthetic pathway, which supplies amino sugars for protein glycosylation, cell-wall synthesis, and signaling. Dysregulation of this activity has been linked to metabolic and stress-related phenotypes, and the enzyme is a target for anti-inflammatory and antimicrobial research [1,8]. Its conservation across species makes it a model for studying enzyme mechanism and regulation [2,7].
• It catalyzes the rate-limiting step of the hexosamine biosynthetic pathway, which produces UDP-N-acetylglucosamine for glycosylation.
• The enzyme is conserved from bacteria to humans, enabling comparative studies of catalysis and regulation [1,2,7].
• Overexpression in yeast confers resistance to methylmercury, linking the activity to heavy-metal stress responses.
• Sex-specific differences in enzyme activity in mouse submandibular gland suggest hormonal or developmental regulation.
• Recombinant human GFAT1 can be purified, supporting drug discovery and structural biology.
• The yeast gene is regulated by pheromone signaling, connecting the activity to developmental programs.
• Anti-inflammatory agents can modulate the activity, indicating pharmacological relevance.
• The enzyme from Thermus thermophilus provides a thermostable model for mechanistic studies.
• Altered flux through this step may affect glycosylation patterns relevant to cell signaling and disease.
• The activity is a potential target for antimicrobial and metabolic therapies [1,8].
Molecular Mechanism of L-glutamine:D-fructose-6-phosphate transaminase (isomerizing) activity
Substrate Binding and Catalytic Reaction
In simple terms: The enzyme grabs two molecules, fructose 6-phosphate and glutamine, and swaps an ammonia-like group from glutamine onto the sugar.
The enzyme binds D-fructose 6-phosphate and L-glutamine and catalyzes the transfer of the amide nitrogen from glutamine to fructose 6-phosphate, yielding D-glucosamine 6-phosphate and L-glutamate. This reaction is the first committed step of the hexosamine biosynthetic pathway. The enzyme is known as glucosamine-6-phosphate synthase or glutamine:fructose-6-phosphate amidotransferase [1,2].
Isomerization Step
In simple terms: After the nitrogen is transferred, the sugar molecule rearranges into its final form.
The reaction is described as isomerizing because the product D-glucosamine 6-phosphate is formed through an isomerization of the fructose 6-phosphate backbone after nitrogen transfer. The overall transformation is a transamination followed by isomerization, as reflected in the official name L-glutamine:D-fructose-6-phosphate transaminase (isomerizing) activity.
Enzyme Sources and Purification
In simple terms: Scientists have purified this enzyme from many organisms to study how it works.
The enzyme has been purified and characterized from rat liver, from the extreme thermophile Thermus thermophilus HB8, and from Saccharomyces cerevisiae. Recombinant human GFAT1 has been expressed and purified as an active His-tagged protein. These preparations enable kinetic and structural analyses of the catalytic mechanism [2,5,7].
Regulation by Cellular Signals
In simple terms: The amount and activity of the enzyme can change in response to signals like pheromones or inflammation.
In yeast, transcription of the gene encoding this activity is regulated by pheromone signaling. In mammals, enzyme activity shows sex differences in the mouse submandibular gland, indicating hormonal or developmental regulation. Anti-inflammatory agents can also affect the activity, suggesting pharmacological modulation.
Role in Stress Resistance
In simple terms: Having more of this enzyme can help cells survive toxic stress.
Overexpression of L-glutamine:D-fructose-6-phosphate amidotransferase in Saccharomyces cerevisiae provides resistance to methylmercury, linking the activity to heavy-metal stress protection. This suggests that the hexosamine pathway contributes to cellular defense mechanisms.
Key Genes Involved in GO:0004360 L-glutamine:D-fructose-6-phosphate transaminase (isomerizing) activity
The following genes and proteins are directly associated with GO:0004360 or its regulation across model organisms and humans.
| Gene | Major Role | Research Relevance |
|---|---|---|
| GFPT1 (human) | Encodes glutamine:fructose-6-phosphate amidotransferase 1, catalyzing GO:0004360 | Recombinant human GFAT1 has been purified for biochemical studies |
| GFPT2 (human) | Encodes a second human isoform of GFAT | Isoform-specific roles in hexosamine pathway flux |
| GFA1 (Saccharomyces cerevisiae) | Yeast gene encoding glucosamine-6-phosphate synthase | Pheromonal regulation of transcription; overexpression confers methylmercury resistance |
| glmS (bacteria) | Bacterial glucosamine-6-phosphate synthase | Model for enzyme mechanism and antimicrobial targeting |
| GFAT (rat) | Rat liver glutamine:fructose-6-phosphate amidotransferase | Purification and characterization |
| GFAT (Thermus thermophilus) | Thermostable enzyme from extreme thermophile | Characterization of thermophilic enzyme |
| GFAT (mouse) | Mouse submandibular gland enzyme | Sex difference in activity |
| GFPT1 (mouse) | Mouse ortholog of human GFPT1 | Tissue-specific expression studies |
| UAP1 | UDP-N-acetylglucosamine pyrophosphorylase, downstream of GO:0004360 | Hexosamine pathway flux |
| GNPNAT1 | Glucosamine-phosphate N-acetyltransferase, downstream enzyme | Amino sugar metabolism |
| PGM3 | Phosphoglucomutase 3, involved in UDP-GlcNAc synthesis | Glycosylation disorders |
| O-GlcNAc transferase (OGT) | Adds O-GlcNAc to proteins using UDP-GlcNAc | Signaling and stress responses |
| O-GlcNAcase (OGA) | Removes O-GlcNAc from proteins | Glycosylation dynamics |
| GFAT1 (Drosophila) | Invertebrate ortholog | Developmental studies |
| GFAT (C. elegans) | Nematode ortholog | Metabolic and stress studies |
| GFAT (zebrafish) | Vertebrate ortholog | Developmental glycosylation |
| GFAT (plant) | Plant ortholog | Cell-wall biosynthesis |
| GFAT (fungal) | Fungal ortholog | Antifungal target |
How Is L-glutamine:D-fructose-6-phosphate transaminase (isomerizing) activity Regulated?
The activity of L-glutamine:D-fructose-6-phosphate transaminase (isomerizing) is regulated at multiple levels. In yeast, transcription of the encoding gene is controlled by pheromone signaling, linking the activity to mating and developmental programs. In mammals, enzyme activity shows sex-specific differences in the mouse submandibular gland, suggesting hormonal regulation. Anti-inflammatory agents can modulate the activity, indicating pharmacological control. Additionally, the enzyme is the rate-limiting step of the hexosamine pathway, so its flux is sensitive to substrate availability and feedback from downstream metabolites.
L-glutamine:D-fructose-6-phosphate transaminase (isomerizing) activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| GFPT1 | Metabolic and glycosylation disorders | Knockout and knock-in cell models [1,5] |
| GFA1 (yeast) | Heavy-metal stress resistance | Overexpression in S. cerevisiae |
| GFAT (mouse) | Sex-specific submandibular gland biology | Mouse knockout or point-mutation models |
| GFAT (Thermus thermophilus) | Thermostable enzyme mechanism | Recombinant expression and mutagenesis |
| GFPT1 (human) | Inflammation-related pathways | Cell-based assays with anti-inflammatory agents |
Metabolic and Glycosylation Disorders
Altered flux through GO:0004360 affects the hexosamine biosynthetic pathway and downstream protein glycosylation, which is relevant to metabolic and congenital disorders of glycosylation. The enzyme is a potential target for modulating glycosylation in disease.
Heavy-Metal Stress and Detoxification
Overexpression of the enzyme in Saccharomyces cerevisiae confers resistance to methylmercury, suggesting a protective role against heavy-metal toxicity. This links the activity to cellular stress defense mechanisms.
Inflammation and Pharmacological Modulation
Anti-inflammatory agents can affect L-glutamine:D-fructose-6-phosphate transaminase activity, indicating that the enzyme may be a target for anti-inflammatory strategies. Further studies are needed to define its therapeutic potential.
Developmental and Sex-Specific Biology
Sex differences in enzyme activity in the mouse submandibular gland suggest roles in sexually dimorphic development or physiology. This highlights the importance of considering sex as a biological variable in studies of GO:0004360.
From L-glutamine:D-fructose-6-phosphate transaminase (isomerizing) activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| What is the catalytic mechanism of GO:0004360? | Recombinant human GFAT1 purified from expression systems |
| How does the enzyme contribute to stress resistance? | Overexpression of GFA1 in Saccharomyces cerevisiae |
| Is the enzyme regulated by pheromone signaling? | Yeast GFA1 transcriptional reporters |
| What are the sex-specific differences in activity? | Mouse submandibular gland models |
| Can anti-inflammatory agents modulate the activity? | Enzyme activity assays with pharmacological compounds |
| How conserved is the enzyme across species? | Purification from rat liver and Thermus thermophilus [2,7] |
How to Study the L-glutamine:D-fructose-6-phosphate transaminase (isomerizing) activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Enzyme activity assay | Conversion of fructose 6-phosphate and glutamine to products | Kinetic characterization of GO:0004360 [1,2] |
| Recombinant expression | Production of active enzyme | Purification of human GFAT1 |
| Western blot | Protein expression levels | Detection of GFAT in tissues |
| qRT-PCR | mRNA levels | Transcriptional regulation by pheromones |
| Overexpression in yeast | Phenotypic resistance | Methylmercury resistance |
| Tissue activity assay | Enzyme activity in extracts | Sex differences in mouse submandibular gland |
| Pharmacological inhibition | Effect of compounds on activity | Anti-inflammatory agent testing |
| Thermostability assay | Enzyme stability at high temperature | Characterization of thermophilic enzyme |
Enzyme Activity Assays
Direct measurement of GO:0004360 activity uses substrates D-fructose 6-phosphate and L-glutamine and detects products D-glucosamine 6-phosphate or L-glutamate [1,2]. These assays are used to characterize kinetics, inhibitors, and species-specific properties [2,7].
Recombinant Protein Expression and Purification
Human GFAT1 can be expressed as an active His-tagged protein and purified for biochemical studies. Similar approaches have been used for the rat liver and Thermus thermophilus enzymes [2,7].
Transcriptional and Genetic Regulation Studies
In yeast, transcriptional regulation by pheromone signaling has been studied using gene expression analysis. Overexpression and knockout approaches reveal phenotypic consequences such as methylmercury resistance.
Tissue-Specific and Sex-Specific Analyses
Enzyme activity measurements in mouse submandibular gland have revealed sex differences. Such studies require careful tissue dissection and activity assays.
How CRISPR Can Be Used to Study GO:0004360 L-glutamine:D-fructose-6-phosphate transaminase (isomerizing) activity
Knockout
CRISPR knockout of GFPT1 or GFPT2 can eliminate GO:0004360 activity in cells, allowing researchers to study the consequences for hexosamine pathway flux, glycosylation, and stress responses [1,5]. Knockout models are essential for determining whether the activity is required for specific phenotypes.
Point Mutation
Point mutations can be introduced into the catalytic domain of GFPT1 to dissect the mechanism of GO:0004360, including substrate binding and isomerization steps [1,5]. Such mutants help identify residues critical for catalysis.
Knock-in
Knock-in of tagged or reporter versions of GFPT1 allows visualization and quantification of the enzyme in live cells. This approach can also be used to introduce disease-associated variants.
Overexpression
CRISPR activation or cDNA overexpression of GFPT1 or GFA1 increases GO:0004360 activity, enabling studies of pathway saturation, stress resistance, and metabolic reprogramming [3,5]. Overexpression in yeast confers methylmercury resistance.
How EDITGENE Supports L-glutamine:D-fructose-6-phosphate transaminase (isomerizing) activity Research
Researchers studying L-glutamine:D-fructose-6-phosphate transaminase (isomerizing) activity-related genes often need to determine whether a candidate gene is causally involved in hexosamine pathway flux, glycosylation, or stress responses. EDITGENE provides CRISPR-based cell model services to enable these functional studies.
Contact EDITGENE today to design your custom CRISPR model for L-glutamine:D-fructose-6-phosphate transaminase (isomerizing) activity research.
Frequently Asked Questions About L-glutamine:D-fructose-6-phosphate transaminase (isomerizing) activity
What is GO:0004360?
GO:0004360 is the Gene Ontology molecular function term for L-glutamine:D-fructose-6-phosphate transaminase (isomerizing) activity, which catalyzes the reaction D-fructose 6-phosphate + L-glutamine = D-glucosamine 6-phosphate + L-glutamate.
What genes are involved in L-glutamine:D-fructose-6-phosphate transaminase (isomerizing) activity?
The main genes are GFPT1 and GFPT2 in humans, GFA1 in yeast, and glmS in bacteria, all encoding glucosamine-6-phosphate synthase or GFAT [1,5,6].
What is the function of glucosamine-6-phosphate synthase?
It catalyzes the first committed step of the hexosamine biosynthetic pathway, producing glucosamine 6-phosphate for amino sugar metabolism.
How is GO:0004360 regulated?
It is regulated transcriptionally by pheromone signaling in yeast, by sex-specific factors in mouse submandibular gland, and pharmacologically by anti-inflammatory agents [4,6,8].
What diseases are associated with GO:0004360?
Altered activity is linked to metabolic and glycosylation disorders, heavy-metal stress responses, and inflammation-related pathways [1,3,8].
Can CRISPR be used to study GO:0004360?
Yes, CRISPR knockout, point mutation, knock-in, and overexpression models can be used to study the enzyme's function and regulation [1,5].
What is the reaction catalyzed by GO:0004360?
D-fructose 6-phosphate + L-glutamine = D-glucosamine 6-phosphate + L-glutamate.
Which organisms have this enzyme?
It is conserved from bacteria such as Thermus thermophilus and yeast to mammals including rat, mouse, and human [1,2,3,4,5,6,7].
How can I measure GO:0004360 activity?
Enzyme activity assays using fructose 6-phosphate and glutamine as substrates, often with purified recombinant enzyme, are standard [1,2,5].
What is the role of GFAT in methylmercury resistance?
Overexpression of L-glutamine:D-fructose-6-phosphate amidotransferase in Saccharomyces cerevisiae provides resistance to methylmercury.
Conclusion
GO:0004360, L-glutamine:D-fructose-6-phosphate transaminase (isomerizing) activity, is a conserved molecular function that controls the first step of the hexosamine biosynthetic pathway. Its study spans enzymology, stress biology, and metabolic regulation, with tools ranging from purified recombinant proteins to CRISPR-engineered cell models [1,2,5]. Understanding this activity provides insights into glycosylation, cellular stress responses, and potential therapeutic targets [1,3,8].
References
- 1. Milewski S. 2002. Glucosamine-6-phosphate synthase--the multi-facets enzyme.. Biochim Biophys Acta 1597(2):173-92 PMID: 12044898
- 2. Huynh QK et al.. 2000. Purification and characterization of glutamine:fructose 6-phosphate amidotransferase from rat liver.. Arch Biochem Biophys 379(2):307-13 PMID: 10898949
- 3. Miura N et al.. 1999. Overexpression of L-glutamine:D-fructose-6-phosphate amidotransferase provides resistance to methylmercury in Saccharomyces cerevisiae.. FEBS Lett 458(2):215-8 PMID: 10481068
- 4. Hosoi K et al.. 1978. Sex difference in L-glutamine D-fructose-6-phosphate aminotransferase activity of mouse submandibular gland.. Biochim Biophys Acta 543(3):283-92 PMID: 708787
- 5. Richez C et al.. 2007. Expression and purification of active human internal His(6)-tagged L-glutamine: D-Fructose-6P amidotransferase I.. Protein Expr Purif 54(1):45-53 PMID: 17379537
- 6. Watzele G et al.. 1989. Cloning of the glutamine:fructose-6-phosphate amidotransferase gene from yeast. Pheromonal regulation of its transcription.. J Biol Chem 264(15):8753-8 PMID: 2656689
- 7. Badet-Denisot MA et al.. 1997. Characterization of L-glutamine:D-fructose-6-phosphate amidotransferase from an extreme thermophile Thermus thermophilus HB8.. Arch Biochem Biophys 337(1):129-36 PMID: 8990277
- 8. Chatterjee SS et al.. 1976. Effect of anti-inflammatory agent on L-glutamine-D-fructose-6-phosphate transaminase.. Arzneimittelforschung 26(4):502-5 PMID: 1085150
