GO:0016744 transketolase or transaldolase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0016744 (transketolase or transaldolase activity) describes catalysis of aldehyde or ketonic group transfer between donor and acceptor compounds, a core reaction of the nonoxidative pentose phosphate pathway.
• Transketolase (TKT) and transaldolase (TALDO1) are the principal human enzymes carrying this activity, interconverting pentose and hexose phosphates to support ribose-5-phosphate and NADPH supply.
• Erythrocyte transketolase activity is a long-established functional readout used in clinical and metabolic studies, including suspected Leigh's disease.
• Substrate inhibition and stereochemical control are key kinetic features of transketolase that shape its use in biocatalysis and metabolic engineering.
• Nonoxidative pentose phosphate pathway flux through transketolase/transaldolase regulates CD8+ T cell immunity by maintaining NADPH homeostasis.
• Ribose-5-phosphate metabolism, which depends on transketolase/transaldolase activity, protects E. coli from antibiotic lethality.
Description
GO:0016744, transketolase or transaldolase activity, is a molecular function defined as catalysis of the transfer of an aldehyde or ketonic group from one compound (donor) to another (acceptor). This activity is best known from the nonoxidative branch of the pentose phosphate pathway, where transketolase and transaldolase interconvert sugar phosphates to balance ribose-5-phosphate and NADPH production. Because these reactions sit at the intersection of nucleotide biosynthesis, redox homeostasis and central carbon metabolism, they are studied across enzymology, immunology, microbiology and clinical diagnostics. Transketolase activity has been measured in human erythrocytes for decades, and such assays remain a practical functional window into this GO term in patient samples. In parallel, mechanistic and engineering studies have defined substrate inhibition, cofactor requirements and stereoselectivity of transketolase, making it a model enzyme for aldehyde/ketonic group transfer. The term therefore matters both as a fundamental catalytic concept and as a pathway node with measurable physiological consequences.
transketolase or transaldolase activity At A Glance
| GO ID | GO:0016744 |
|---|---|
| GO term | transketolase or transaldolase activity |
| Ontology | molecular_function |
| Synonym | transferase activity, transferring aldehyde or ketonic groups |
| Definition | Catalysis of the transfer of an aldehyde or ketonic group from one compound (donor) to another (acceptor). |
| Major function | Aldehyde/ketonic group transfer in sugar-phosphate interconversion and related metabolic reactions. |
| Representative enzymes | Transketolase (TKT) and transaldolase (TALDO1). |
| Pathway context | Nonoxidative pentose phosphate pathway. |
| Clinical readout | Erythrocyte transketolase activity. |
What Is GO:0016744?
In practical terms, GO:0016744 covers enzymes that move an aldehyde or ketonic group from a donor molecule to an acceptor molecule. The canonical examples are transketolase and transaldolase, which catalyze such transfers on phosphorylated sugars in the nonoxidative pentose phosphate pathway. The synonym 'transferase activity, transferring aldehyde or ketonic groups' captures the same chemistry.
Why Is transketolase or transaldolase activity Important in Cell Biology?
GO:0016744 is important because it defines the catalytic step that links sugar-phosphate rearrangement to two essential outputs: ribose-5-phosphate for nucleotide synthesis and NADPH for reductive biosynthesis and antioxidant defense. Perturbing this activity changes metabolic flux, redox balance and cell survival, which is why it is studied in immunometabolism, microbial antibiotic responses and inherited metabolic disease. The same chemistry also underpins biocatalytic routes to chiral alpha-hydroxyketones, making the term relevant to synthetic biology and enzyme engineering.
• Supports ribose-5-phosphate supply for nucleotide and nucleic acid biosynthesis.
• Contributes to NADPH homeostasis, which is required for CD8+ T cell immunity.
• Erythrocyte transketolase activity is a measurable functional marker in clinical investigations.
• Transketolase kinetics, including substrate inhibition, inform metabolic modeling and enzyme engineering.
• Engineered transketolase variants enable stereoselective alpha-hydroxyketone synthesis.
• Ribose-5-phosphate metabolism protects E. coli from antibiotic lethality.
• The nonoxidative pentose phosphate pathway is a metabolic vulnerability in immune cell function.
• The term provides a defined functional annotation for interpreting enzyme assays and omics data.
Molecular Mechanism of transketolase or transaldolase activity
Donor-acceptor chemistry
In simple terms: One molecule hands over a small chemical group to another molecule.
GO:0016744 is defined by transfer of an aldehyde or ketonic group from a donor compound to an acceptor compound. In the pentose phosphate pathway, this chemistry rearranges sugar phosphates rather than degrading them, allowing carbon skeletons to be reshuffled between pools.
Transketolase reaction and cofactor dependence
In simple terms: Transketolase uses a helper molecule to move a two-carbon unit between sugars.
Transketolase from yeast, rat liver and pig liver has been purified and characterized as a classic aldehyde-transfer enzyme. Its catalytic cycle depends on a thiamine-derived cofactor, and detailed kinetic work has documented substrate inhibition as a regulatory feature of the enzyme.
Transaldolase reaction
In simple terms: Transaldolase moves a three-carbon unit to rebalance sugar phosphates.
Transaldolase acts alongside transketolase in the nonoxidative pentose phosphate pathway to interconvert pentose and hexose phosphates. Together these reactions determine how much carbon flows toward ribose-5-phosphate versus glycolytic intermediates.
Substrate inhibition and kinetic control
In simple terms: Too much substrate can slow the enzyme down.
Substrate inhibition of transketolase has been experimentally described, showing that the enzyme does not simply follow saturating Michaelis-Menten behavior at high substrate concentrations. This kinetic property is important when interpreting flux measurements and when designing biocatalytic reactions.
Stereochemical outcome and engineering
In simple terms: The enzyme can be tuned to make one mirror-image product preferentially.
Engineering of transketolase has been pursued to achieve stereoselective alpha-hydroxyketone synthesis, demonstrating that the catalytic scaffold can be modified for defined product configurations. Such work connects the GO term to applied enzyme design.
Pathway-level regulation by demand
In simple terms: The reaction rate follows what the cell needs.
Nonoxidative pentose phosphate pathway flux through transketolase/transaldolase supports NADPH homeostasis in CD8+ T cells, indicating that activity is tuned to redox demand. In bacteria, ribose-5-phosphate metabolism influences survival under antibiotic stress, linking this activity to stress responses.
Key Genes Involved in GO:0016744 transketolase or transaldolase activity
The genes and proteins most directly associated with GO:0016744 are the transketolase and transaldolase enzymes and their pathway partners.
| Gene | Major Role | Research Relevance |
|---|---|---|
| TKT | Transketolase; aldehyde group transfer in pentose phosphate pathway | Core enzyme for GO:0016744 assays and metabolic studies |
| TALDO1 | Transaldolase; ketonic group transfer in pentose phosphate pathway | Pathway partner for nonoxidative flux and NADPH balance |
| RPE | Ribulose-5-phosphate 3-epimerase; supplies transketolase substrate | Upstream step feeding transketolase reactions |
| RPIA | Ribose-5-phosphate isomerase; interconverts ribose and ribulose phosphates | Controls ribose-5-phosphate availability for transketolase/transaldolase |
| G6PD | Glucose-6-phosphate dehydrogenase; oxidative pentose phosphate pathway entry | Provides NADPH and pathway input relevant to nonoxidative branch |
| PGD | 6-phosphogluconate dehydrogenase; oxidative pentose phosphate pathway | Supplies ribulose-5-phosphate for nonoxidative reactions |
| PRPS1 | Phosphoribosyl pyrophosphate synthetase 1; uses ribose-5-phosphate | Connects transketolase/transaldolase output to nucleotide synthesis |
| PRPS2 | Phosphoribosyl pyrophosphate synthetase 2; uses ribose-5-phosphate | Links pentose phosphate output to nucleotide metabolism |
| TKTL1 | Transketolase-like 1; related transketolase family protein | Studied in metabolic reprogramming contexts |
| TKTL2 | Transketolase-like 2; related transketolase family protein | Family member relevant to transketolase biology |
| SLC19A2 | Thiamine transporter; supports cofactor supply | Thiamine availability affects transketolase-dependent reactions |
| SLC19A3 | Thiamine transporter; supports cofactor supply | Relevant to thiamine-dependent enzyme function |
| SLC25A19 | Mitochondrial thiamine pyrophosphate carrier | Supports cofactor pools for thiamine-dependent enzymes |
| ALDOA | Fructose-bisphosphate aldolase A; glycolytic carbon flux | Context for how pentose phosphate intermediates are consumed |
| GAPDH | Glyceraldehyde-3-phosphate dehydrogenase; glycolytic enzyme | Shares glyceraldehyde-3-phosphate intermediate with transketolase output |
| PFKM | Phosphofructokinase; glycolytic commitment step | Helps interpret competition between glycolysis and pentose phosphate pathway |
| TPI1 | Triosephosphate isomerase; glycolytic interconversion | Relevant to routing of transketolase/transaldolase products |
| NNT | Nicotinamide nucleotide transhydrogenase; NADPH-related redox | Context for NADPH homeostasis linked to pathway flux |
How Is transketolase or transaldolase activity Regulated?
Transketolase and transaldolase activity is regulated at multiple levels. Kinetically, transketolase shows substrate inhibition, meaning high substrate concentrations reduce activity rather than simply saturating the enzyme. Metabolically, flux through the nonoxidative pentose phosphate pathway is adjusted to maintain NADPH homeostasis, as shown in CD8+ T cells where this pathway supports immune function. In bacteria, ribose-5-phosphate metabolism influences survival during antibiotic exposure, indicating stress-responsive control of the same pathway. Cofactor availability, particularly thiamine-derived cofactors, is also required for transketolase catalysis.
transketolase or transaldolase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| TKT | Leigh's disease / subacute necrotising encephalomyelopathy (erythrocyte activity readout) | Patient erythrocyte transketolase activity assay |
| TKT | CD8+ T cell immunity via NADPH homeostasis | T cell metabolic perturbation models |
| TALDO1 | Nonoxidative pentose phosphate pathway flux and redox balance | Metabolic flux analysis in cell models |
| RPE/RPIA | Ribose-5-phosphate metabolism and antibiotic lethality | E. coli genetic perturbation models |
| TKTL1 | Metabolic reprogramming in proliferative cells | Transketolase-family expression and activity studies |
Leigh's disease and suspected subacute necrotising encephalomyelopathy
Erythrocyte transketolase activity has been measured in suspected cases of Leigh's disease, or subacute necrotising encephalomyelopathy, as part of clinical metabolic evaluation. This reflects the use of transketolase activity as a functional readout in patients with suspected energy-metabolism disorders.
Immunometabolism and CD8+ T cell immunity
The nonoxidative pentose phosphate pathway, which depends on transketolase/transaldolase activity, regulates CD8+ T cell immunity by maintaining NADPH homeostasis. This links GO:0016744 to immune cell function and to metabolic control of adaptive immunity.
Antibiotic lethality and bacterial stress responses
Ribose-5-phosphate metabolism protects E. coli from antibiotic lethality, implicating transketolase/transaldolase-dependent reactions in bacterial survival under drug stress. This has implications for understanding antibiotic efficacy and resistance.
Clinical enzymology and diagnostic measurement
Erythrocyte transketolase has been described in Japanese clinical reference literature as a measurable enzyme activity, supporting its use in diagnostic workflows. Such measurements provide a direct functional assessment related to GO:0016744.
From transketolase or transaldolase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of transketolase activity alter NADPH homeostasis? | TKT knockout cell model |
| Does transaldolase loss change nonoxidative pentose phosphate flux? | TALDO1 knockout cell model |
| Can a specific catalytic residue be tested for aldehyde transfer? | Point-mutation knock-in of TKT |
| Can a tagged enzyme be tracked in live cells? | Tagged knock-in of TKT or TALDO1 |
| Does increased transketolase activity change metabolite pools? | Overexpression cell model |
| Does ribose-5-phosphate metabolism affect antibiotic survival? | Bacterial knockout or overexpression models |
How to Study the transketolase or transaldolase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Erythrocyte transketolase assay | Functional transketolase activity in patient samples | Clinical metabolic evaluation |
| Purified enzyme kinetics | Rate behavior, substrate inhibition | Enzyme characterization |
| Metabolite profiling | Pentose phosphate pathway intermediates | Pathway flux studies |
| NADPH measurement | Redox homeostasis | Immunometabolism experiments |
| Antibiotic survival assays | Bacterial stress response | Ribose-5-phosphate metabolism studies |
| Mutagenesis and product analysis | Stereoselectivity of alpha-hydroxyketone synthesis | Enzyme engineering |
| Gene expression analysis | TKT/TALDO1 transcript levels | Contextualizing activity changes |
| Isotope tracing | Carbon flow through nonoxidative pentose phosphate pathway | Metabolic flux analysis |
Enzyme activity assays
Transketolase activity can be measured directly in erythrocytes and other samples, providing a functional readout of GO:0016744. Purified enzyme preparations from yeast, rat liver and pig liver have been used to define assay conditions and catalytic properties.
Kinetic characterization
Kinetic studies reveal substrate inhibition and other rate behaviors of transketolase, which are essential for interpreting activity data. Such experiments distinguish simple saturation from inhibitory regimes at high substrate concentrations.
Metabolic flux and metabolomics
Nonoxidative pentose phosphate pathway flux can be inferred from metabolite labeling and pool sizes, linking transketolase/transaldolase activity to NADPH homeostasis and ribose-5-phosphate supply. These approaches connect enzyme activity to pathway-level phenotypes.
Protein engineering and biocatalysis
Engineering transketolase for stereoselective alpha-hydroxyketone synthesis demonstrates how activity can be redirected for synthetic applications. This combines mutagenesis with product analysis to quantify stereochemical outcomes.
How CRISPR Can Be Used to Study GO:0016744 transketolase or transaldolase activity
Knockout
CRISPR knockout of TKT or TALDO1 can be used to test whether loss of transketolase or transaldolase activity disrupts NADPH homeostasis and ribose-5-phosphate supply. Such models help determine the causal contribution of GO:0016744 to metabolic and immune phenotypes.
Point Mutation
Point mutations in catalytic residues of transketolase can be introduced to dissect aldehyde transfer chemistry and cofactor dependence. These models allow separation of catalytic activity from protein abundance effects.
Knock-in
Knock-in of tagged TKT or TALDO1 enables tracking of enzyme localization and interaction partners while preserving endogenous regulation. This is useful for linking the GO term to cellular context.
Overexpression
Overexpression of transketolase or transaldolase can be used to test whether increased activity alters pathway flux, NADPH levels or stress survival. Such models complement loss-of-function studies.
How EDITGENE Supports transketolase or transaldolase activity Research
Researchers studying transketolase or transaldolase activity-related genes often need to determine whether a candidate gene is causally involved in a metabolic, immune or stress phenotype, and CRISPR-based models provide a direct way to test that causality.
Contact EDITGENE today to design your custom CRISPR model for transketolase or transaldolase activity research.
Frequently Asked Questions About transketolase or transaldolase activity
What is GO:0016744 transketolase or transaldolase activity?
GO:0016744 is a molecular function term describing catalysis of the transfer of an aldehyde or ketonic group from one compound (donor) to another (acceptor).
What genes are involved in transketolase or transaldolase activity?
The principal genes are TKT, encoding transketolase, and TALDO1, encoding transaldolase, with pathway partners such as RPE and RPIA supporting the reactions.
What does transketolase do in the pentose phosphate pathway?
Transketolase transfers aldehyde groups between sugar phosphates in the nonoxidative pentose phosphate pathway, helping balance ribose-5-phosphate and NADPH production.
How is transketolase activity measured?
Transketolase activity can be measured in erythrocytes and in purified enzyme preparations, with assays used in clinical and biochemical studies.
Why is erythrocyte transketolase activity clinically relevant?
Erythrocyte transketolase activity has been measured in suspected cases of Leigh's disease or subacute necrotising encephalomyelopathy as a functional metabolic readout.
Does transketolase show substrate inhibition?
Yes, substrate inhibition of transketolase has been experimentally described, meaning high substrate levels can reduce activity.
How does transketolase relate to immunity?
The nonoxidative pentose phosphate pathway regulates CD8+ T cell immunity by maintaining NADPH homeostasis, linking transketolase/transaldolase activity to immune function.
Can transketolase be engineered for chemical synthesis?
Yes, transketolase has been engineered for stereoselective alpha-hydroxyketone synthesis.
What is the role of ribose-5-phosphate metabolism in bacteria?
Ribose-5-phosphate metabolism protects E. coli from antibiotic lethality, implicating transketolase/transaldolase-dependent reactions in survival under antibiotic stress.
What CRISPR models are useful for studying transketolase or transaldolase activity?
Knockout, point-mutation, knock-in and overexpression models of TKT and TALDO1 are useful for testing causality and mechanism.
Conclusion
GO:0016744, transketolase or transaldolase activity, defines a central aldehyde/ketonic group transfer reaction that connects sugar-phosphate metabolism to nucleotide synthesis and redox balance. Its importance spans clinical enzymology, immunometabolism, microbial stress responses and enzyme engineering. CRISPR-based knockout, point-mutation, knock-in and overexpression models provide direct ways to test how this activity contributes to disease and cell biology.
References
- 1. McBurney A et al.. 1980. Erythrocyte transketolase activity in suspected cases of Leigh's disease, or subacute necrotising encephalomyelopathy.. Arch Dis Child 55(10):789-94 PMID: 7436444
- 2. Kochetov GA. 1982. Transketolase from yeast, rat liver, and pig liver.. Methods Enzymol 90 Pt E:209-23 PMID: 6759853
- 3. Solovjeva ON et al.. 2016. Substrate inhibition of transketolase.. Biochim Biophys Acta 1864(3):280-282 PMID: 26708478
- 4. Yin X et al.. 2025. Engineering transketolase for stereoselective α-hydroxyketone synthesis.. Methods Enzymol 722:447-472 PMID: 41203356
- 5. Feng J et al.. 2026. Nonoxidative pentose phosphate pathway regulates CD8(+) T cell immunity by maintaining NADPH homeostasis.. Proc Natl Acad Sci U S A 123(8):e2526325123 PMID: 41719332
- 6. Seregina T et al.. 2025. Ribose-5-phosphate metabolism protects E. coli from antibiotic lethality.. mBio 16(8):e0065425 PMID: 40600718
- 7. Yasuda K et al.. 1995. [Erythrocyte transketolase].. Nihon Rinsho 53 Su Pt 2:258-61 PMID: 8753231
- 8. Yasuda K et al.. 2004. [Erythrocyte transketolase].. Nihon Rinsho 62 Suppl 12:823-6 PMID: 15658460
