Biochemistry · Molecule
Squalene !
Squalene is a linear 30-carbon hydrocarbon, with no oxygen, that folds up to form the first sterol.
Updated 2026-11-01
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Key facts
- It forms when two farnesyl pyrophosphates (C15) are joined tail-to-tail with NADPH (squalene synthase).
- It is the first intermediate used only for sterols: earlier ones also feed other isoprenoids.
- Squalene epoxidase oxidises it to 2,3-oxidosqualene, which lanosterol synthase cyclises.
- Formula
- C₃₀H₅₀
- PubChem
- CID 638072
Structure
- Six isoprene units with six trans double bonds; very hydrophobic.
- It is abundant in shark-liver oil (hence the name, from Squalus) and in human sebum.
Clinical notes
- Fungi treated with terbinafine accumulate squalene, which is toxic to them.
- Squalene emulsions are used as an adjuvant in some vaccines.
Pathways
Related
Test yourself
Think of the answer, then tap the question to see it.
How is squalene formed?
Squalene synthase joins two farnesyl pyrophosphates tail-to-tail using NADPH.
Which enzyme acts on squalene, and which drug blocks it in fungi?
Squalene epoxidase; terbinafine inhibits it in fungi.
Why is squalene called the first sterol-committed intermediate?
Because earlier compounds also make other isoprenoids, while squalene only goes on to sterols.
Molecules are shown in their neutral form, as the databases deposit them; in the cell the acids and phosphates are ionised.
Educational information, not medical advice. For any symptom, see a health professional.
Sources: Squalene (CID 638072) (PubChem, NCBI, 2026) · Public domain; Cholesterol biosynthesis (R-HSA-191273) (Reactome, 2026).
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