Biochemistry · Enzyme
Citrate synthase !
Citrate synthase opens each turn of the Krebs cycle: it joins acetyl-CoA to oxaloacetate to make citrate.
Updated 2026-10-31
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Key facts
- Acetyl-CoA + oxaloacetate + H₂O → citrate + CoA; strongly favoured (thioester hydrolysis drives it).
- A textbook case of induced fit: oxaloacetate closes the enzyme and creates the site for acetyl-CoA.
- Its activity is used as a marker of a tissue's mitochondrial content.
Regulation
- Citrate, succinyl-CoA, NADH and ATP inhibit it; oxaloacetate supply limits it.
Inhibitors and toxins
- Fluoroacetyl-CoA: a false substrate that yields fluorocitrate
Clinical notes
- In fluoroacetate poisoning (the '1080' rodenticide), citrate synthase makes the real poison, fluorocitrate: 'lethal synthesis'.
Pathways
Related conditions
Related
Test yourself
Think of the answer, then tap the question to see it.
Which substrate binds citrate synthase first?
Oxaloacetate; its binding closes the enzyme and forms the acetyl-CoA site.
What is 'lethal synthesis'?
Citrate synthase turns fluoroacetate into fluorocitrate, which blocks aconitase.
Which metabolites inhibit citrate synthase?
Citrate, succinyl-CoA, NADH and ATP.
Educational information, not medical advice. For any symptom, see a health professional.
Sources: CS: Citrate synthase, mitochondrial (human) (UniProt, 2026); Citric acid cycle (TCA cycle) (Reactome, 2026); 2CTS: Citrate synthase with citrate and CoA (RCSB Protein Data Bank, 2026).
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