Page 311 - Biochemistry PharmD General

Cholesterol Biosynthesis Pathway 310

Stage 3: Condensation of six activated
isoprene units to form squalene

Isopentenyl phosphate and dimethylallyl
phosphate undergo a “head-to-tail”
condensation in which one phosphate
group is displaced and a 10-carbon chain
(geranyl phosphate) is formed.

Another “head-to-tail” condensation→ 15-
carbon farnesyl pyrophosphate

Finally, two molecules of farnesyl join head
to head, eliminating the phosphate
groups and forming squalene