[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Biochemistry](https://durgical.com/en/biochemistry/) › Transketolase

[Biochemistry](https://durgical.com/en/biochemistry/) · Enzyme

# Transketolase

Transketolase swaps two-carbon units between sugars in the pentose pathway; it needs thiamine (vitamin B1).

Updated 2026-11-01

Loading the 3D model…

## Key facts

- It moves 2 carbons from a ketose (xylulose 5-phosphate) to an aldose (ribose 5-phosphate or erythrose 4-phosphate).
- Cofactor: thiamine pyrophosphate (TPP), the same as PDH and α-ketoglutarate dehydrogenase.
- It links the pentose pathway with glycolysis in both directions (non-oxidative, reversible phase).
- Structure 3MOS (human) has TPP in the active site.

**EC number**
[2.2.1.1](https://www.enzyme-database.org/query.php?ec=2.2.1.1)

**Genes**
TKT

**Structure (PDB)**
[3MOS](https://www.rcsb.org/structure/3MOS)

## Regulation

- It depends on substrate availability and on thiamine.

## Inhibitors and toxins

- Oxythiamine (thiamine antagonist)

## Clinical notes

- Red cell transketolase activity, before and after adding TPP, measures thiamine deficiency.
- A variant with low affinity for TPP has been linked to higher risk of Wernicke-Korsakoff syndrome in people with alcoholism.
- Biallelic TKT variants cause short stature, developmental delay and congenital heart disease (very rare).

## Pathways

- [Pentose phosphate pathway](https://durgical.com/en/biochemistry/pathways/pentose-phosphate-pathway/)

## Related conditions

- [Wernicke encephalopathy (thiamine deficiency)](https://durgical.com/en/conditions/wernicke-encephalopathy/)

## Related

- [Ribose 5-phosphate](https://durgical.com/en/biochemistry/molecules/ribose-5-phosphate/)
- [Glucose-6-phosphate dehydrogenase (G6PD)](https://durgical.com/en/biochemistry/enzymes/glucose-6-phosphate-dehydrogenase/)
- [Pyruvate dehydrogenase complex (PDH)](https://durgical.com/en/biochemistry/enzymes/pyruvate-dehydrogenase-complex/)
- [α-Ketoglutarate dehydrogenase](https://durgical.com/en/biochemistry/enzymes/ketoglutarate-dehydrogenase/)
- [NADPH](https://durgical.com/en/biochemistry/molecules/nadph/)

## Test yourself

Think of the answer, then tap the question to see it.

## Which vitamin does transketolase need?

Thiamine (B1), as thiamine pyrophosphate.

## How is transketolase used to measure thiamine deficiency?

Its activity is measured in red cells; if it rises a lot when TPP is added, the person was low in thiamine.

## How many carbons does transketolase transfer and how many does transaldolase?

Transketolase transfers 2 and transaldolase 3.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/biochemistry/enzymes/transketolase/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [TKT: Transketolase (human)](https://www.uniprot.org/uniprotkb/P29401/entry) (UniProt, 2026); [3MOS: The structure of human Transketolase](https://www.rcsb.org/structure/3MOS) (RCSB Protein Data Bank, 2026); [Pentose phosphate pathway](https://reactome.org/PathwayBrowser/#/R-HSA-71336) (Reactome, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011).

[← All of biochemistry](https://durgical.com/en/biochemistry/)

## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake

Representative model, for educational purposes only.

---
Source: https://durgical.com/en/biochemistry/enzymes/transketolase/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/biochemistry/enzymes/transketolase/