The Fourth Stage of Synthesis
The Four Ring Steroid Basis From Squalene.
All sterols consist of 4 fused rings, and are alcohols, with the hydroxyl group at C-3.
It can be seen quite easily that the linear squalene molecule
| Squalene
|
can be converted into the 4 fused ring structure of sterols.
| Squalene in position to cyclise
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- Squalene monooxygenase adds 1 oxygen atom to the end of the squalene chain, forming an epoxide.
- NADPH is an electron donor and this reduces the other oxygen of the oxygen molecule to water.
- The double bonds of squalene 2,3-epoxide are positioned such that a concerted reaction can occur, which converts the linear squalene into a cyclic structure, called Lanosterol.
- Lanosterol is then converted to cholesterol.
| Cholesterol
|
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Synthesis of Cholesterol
Third Stage of Synthesis