Cholesterol synthesis Flashcards
What molecule does cholesterol synthesis start with?
Acetyl CoA.
What occurs in the first step?
Synthesis of isopentyl pyrophosphate. Condensation of 3 acetyl CoA molecules to form HMG-CoA. HMG-CoA is converted into mevalonate. Mevalonate is phosphorylated and decarboxylated to produce 3-isopentyl pyrophosphate.
What is the rate limiting step of cholesterol synthesis?
HMG-CoA to Mevalonate. Reduced by NADPH and catalysed by HMG-CoA reductase.
How is HMG-CoA reductase under negative feedback control?
Inhibited by mevalonate, cholesterol and bile salts.
Whats happens to mevalonate?
Phosphorylated and decarboxylated to produce 3-isopentyl pyrophosphate.
Where does synthesis of isopentyl pyrophosphate occur?
In the cytoplasm.
What happens in the second step?
Condensation of 6 isopentyl pyrophosphate molecules to form squalene.
Where does condensation of 6 isopentyl pyrophosphate molecules to form squalene occur?
In the cytoplasm.
What happens in the third step?
Cyclisation and demethylation of squalene by monooxygenases.
Where does cyclisation and demethylation of squalene occur?
Endoplasmic reticulum.
