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

# Glyceraldehyde-3-phosphate dehydrogenase (GAPDH)

GAPDH is the glycolysis enzyme that makes NADH and builds a high-energy bond; arsenic fools it.

Updated 2026-10-31

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## Key facts

- G3P + NAD⁺ + Pi ⇌ 1,3-bisphosphoglycerate + NADH + H⁺ (step 6).
- An active-site cysteine forms a thioester with the substrate; inorganic phosphate breaks it, leaving a high-energy acyl phosphate.
- A tetramer with one NAD⁺ per subunit.

**EC number**
[1.2.1.12](https://www.enzyme-database.org/query.php?ec=1.2.1.12)

**Genes**
GAPDH

**Structure (PDB)**
[1U8F](https://www.rcsb.org/structure/1U8F)

## Regulation

- It depends on NAD⁺ being available: without LDH or shuttles, glycolysis stops here.

## Inhibitors and toxins

- Arsenate (competes with phosphate: no ATP at step 7)
- Iodoacetate and other thiol reagents

## Clinical notes

- In arsenic poisoning, arsenate uncouples glycolysis and arsenite blocks PDH and α-ketoglutarate dehydrogenase.
- Its gene is used as an expression control in the lab because nearly every cell expresses it.

## Pathways

- [Glycolysis](https://durgical.com/en/biochemistry/pathways/glycolysis/)
- [Gluconeogenesis](https://durgical.com/en/biochemistry/pathways/gluconeogenesis/)

## Related conditions

- [Arsenic poisoning](https://durgical.com/en/conditions/arsenic-poisoning/)

## Related

- [NAD⁺ (nicotinamide adenine dinucleotide)](https://durgical.com/en/biochemistry/molecules/nad/)
- [ATP (adenosine triphosphate)](https://durgical.com/en/biochemistry/molecules/atp/)

## Test yourself

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

## Which active-site amino acid of GAPDH forms the intermediate?

A cysteine, which forms a thioester with the substrate.

## Why does arsenate leave glycolysis with no net ATP?

It forms 1-arseno-3-phosphoglycerate, which breaks down on its own: the phosphoglycerate kinase ATP is skipped.

## Which coenzyme does GAPDH reduce?

NAD⁺ to NADH.

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

Sources: [GAPDH: Glyceraldehyde-3-phosphate dehydrogenase (human)](https://www.uniprot.org/uniprotkb/P04406/entry) (UniProt, 2026); [Arsenic](https://www.who.int/news-room/fact-sheets/detail/arsenic) (World Health Organization, 2026); [1U8F: Human placental glyceraldehyde-3-phosphate dehydrogenase](https://www.rcsb.org/structure/1U8F) (RCSB Protein Data Bank, 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.

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Source: https://durgical.com/en/biochemistry/enzymes/glyceraldehyde-3-phosphate-dehydrogenase/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/biochemistry/enzymes/glyceraldehyde-3-phosphate-dehydrogenase/