The synthesis of cholesterol is a long and complex series of reactions. These many reactions can be subdivided into four steps, each with a particular substrate and product.
The synthesis of cholesterol begins with
These simplest building blocks are then converted into
in the first step and include the rate-limiting enzyme HMG-CoA reductase.
The second step involves a decarboxylase and produces
The third step combines several molecules to make
, which is finally acted upon by a monooxygenase and several other enzymes to yield a sterol product (including cholesterol).