Features of cholesterol synthesis
- Acetate of acetyl CoA provides all carbons
- Reducing equivalents are supplied by NADPH and ATP provides energy
- For producing 1 mole of cholesterol, 18 moles of acetyl CoA, 36 moles of ATP and 16 moles of NADPH are required.
There are 5 stages in synthesis of cholesterol
- 2 moles of acetyl CoA combine to form acetoacetylCoA
- Again a mole of acetyl CoA is added to form HMG CoA
- HMG CoA reductase (rate limiting enzyme) catalyses the reduction of HMG CoA to mevalonate
- Mevalonate is converted to 3-phospho5-PPM after 3 step reactio
- 3-phospho-5-PPM on decarboxylation forms Isopentenyl PP
- IPP isomerizes to form dimethylallyl PP
- Geranyl PP is formed by condensation of isopentenyl PP and dimethylallyl PP
- GPP condenses with IPP to form Farnesyl PP
- 2 units of Farnesyl PP unite and get reduced to form squalene
- After undergoing hydroxylation &cyclization Utilizing O2 and NADPH squalene gets converted to lanosterol.
- Lanosterol after 19 enzymatic reactions forms cholesterol.
A way to remember this –
Ariana & Adele with Calvin Harris made a Music video at 5 places on an Island, deserted and green feat. Sharks,lobsters and crabs!
Calvin Harris-HMG CoA
Island – Isopentenyl PP
Hope this helps!
-Anuja Mandavkar, Jay Shah