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.
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
Related conditions
Related
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.
Educational information, not medical advice. For any symptom, see a health professional.
Sources: GAPDH: Glyceraldehyde-3-phosphate dehydrogenase (human) (UniProt, 2026); Arsenic (World Health Organization, 2026); 1U8F: Human placental glyceraldehyde-3-phosphate dehydrogenase (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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