Cholesterol is synthesized from acetyl-CoA in the liver. Cholesterol and a number of natural products from plants (including rubber) are
isoprenoid compounds. The isoprenoid unit is a 5-carbon structure.
Isoprenoid compounds are synthesized from a common intermediate,
mevalonic acid. Mevalonate is synthesized from acetyl-CoA and then serves as the precursor to isoprenoid units.
acetyl-CoA → mevalonate
The key enzyme in this pathway is HMG-CoA reductase in connection with ketone body formation. The reactions leading to HMG-CoA are shared with that pathway.
Acetyl-CoA can be derived directly from metabolism, especially lipid degradation, or by the acetate thiokinase reaction:
Two acetyl-CoA molecules condense to form acetoacetyl-CoA.
Finally, the enzyme 3-hydroxy-3-methylglutaryl-CoA synthase (HMG-CoA synthase) adds a third acetyl-CoA.
Fatty Acid Oxidation
Lipid Biosynthesis
