Transketolase !

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

Updated 2026-11-01

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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.

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).

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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.

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

Sources: TKT: Transketolase (human) (UniProt, 2026); 3MOS: The structure of human Transketolase (RCSB Protein Data Bank, 2026); Pentose phosphate pathway (Reactome, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011).

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Representative model, for educational purposes only.