Biochemistry · Enzyme
LCAT (lecithin–cholesterol acyltransferase) !
LCAT esterifies free cholesterol on HDL; the ester sinks into the particle core, which matures from a disc into a sphere.
Updated 2026-11-01
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Key facts
- Moves a fatty acid from lecithin (phosphatidylcholine) to cholesterol: makes cholesteryl ester and lysolecithin.
- The liver makes it and it circulates in plasma; HDL ApoA-I activates it.
- Turns nascent (discoidal) HDL into mature spherical HDL and keeps the gradient that lets HDL keep taking up cholesterol.
- It is a key step of reverse cholesterol transport.
Structure
- An α/β-hydrolase fold with a catalytic serine in a pocket covered by a lid.
- Structure 6MVD holds human LCAT with a fluorophosphonate covalently bound to the active-site serine plus a small activator.
Regulation
- ApoA-I is its main activator.
- It acts mainly on HDL (alpha activity) and less on LDL (beta activity).
Inhibitors and toxins
- Fluorophosphonates such as IDFP (experimental)
Clinical notes
- Familial LCAT deficiency causes corneal clouding, anaemia and progressive kidney damage with very low HDL; the partial form (fish-eye disease) mainly affects the cornea.
- Severe liver disease lowers its activity and disturbs the lipoproteins.
- Without LCAT free cholesterol builds up in red-cell membranes (target cells).
Related conditions
Related
- HDL (high-density lipoprotein)
- Cholesterol
- Lipoprotein metabolism
- CETP (cholesteryl ester transfer protein)
Test yourself
Think of the answer, then tap the question to see it.
What reaction does LCAT catalyse?
It transfers a fatty acid from lecithin to cholesterol: cholesteryl ester and lysolecithin.
Which apolipoprotein activates LCAT?
HDL's ApoA-I.
Why does LCAT help HDL keep taking up cholesterol?
Esterifying it hides it in the core: surface free cholesterol falls and the gradient from cells is kept.
Educational information, not medical advice. For any symptom, see a health professional.
Sources: LCAT: Phosphatidylcholine-sterol acyltransferase (human) (UniProt, 2026); LCAT gene: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2026); 6MVD: Crystal structure of Lecithin:cholesterol acyltransferase (LCAT) in complex with isopropyl dodec-11-enylfluorophosphonate (IDFP) and a small molecule activator (RCSB Protein Data Bank, 2026); Plasma lipoprotein remodeling (R-HSA-8963899) (Reactome, 2026).
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Representative model, for educational purposes only.