11. Squalene epoxide is then converted to lanosterol by lanosterol synthase.

Biosynthesis of Cholesterol:
Biochemical Aspects

CoA

O

O

S

H2O

CoA

CoA

O

S

+

Acetyl-CoA

Acetoacetyl-CoA

1. Condensation of Acetyl-CoA and Acetoacetyl-CoA, catalyzed by HMG-CoA synthase, forms HMG-CoA (3-hydroxy-3-methylglutaryl-CoA).

1.

5. 5-pyrophosphomevalonate to 3-isopentenyl pyrophosphate (IPP) by mevalonate-5-pyrophosphate decarboxylase.

7. Catalyzed by prenyl transferase (farnesyl pyrophosphate synthase) dimethylallyl pyrophosphate undergoes reaction with 3-isopentenyl pyrophosphate to form geranyl pyrophosphate.

8. Catalyzed by prenyl transferase (farnesyl pyrophosphate synthase) dimethylallyl pyrophosphate undergoes reaction with 3-isopentenyl pyrophosphate to form geranyl pyrophosphate.

6. Isopentenyl pyrophosphate isomerase catalyzes isomerization of IPP to dimethylallyl pyrophosphate.
Text Box: O Text Box: O Text Box: O- Text Box: O Text Box: O Text Box: O Text Box: O Text Box: O Text Box: O Text Box: O-

9. 3-isopentenyl pyrophosphate reacts with geranyl pyrophosphate forming farnesyl pyrophosphate. (This reaction is also catalyzed by prenyl transferase.)

10. Two molecules of farnesyl pyrophosphate condense to form squalene using squalene synthase.
Text Box: O