Cholesterol 7 alpha-hydroxylase

Cholesterol 7 alpha-hydroxylase also known as cholesterol 7-alpha-monooxygenase or cytochrome P450 7A1 (CYP7A1) is an is_associated_with::enzyme that in humans is encoded by the CYP7A1 is_associated_with::gene.

Function
Cholesterol 7 alpha-hydroxylase is the is_associated_with::rate-limiting enzyme in the synthesis of is_associated_with::bile acid from is_associated_with::cholesterol via the classic pathway, catalyzing the formation of is_associated_with::7-alpha-hydroxycholesterol. CYP7A1 is a is_associated_with::cytochrome P450 is_associated_with::heme is_associated_with::enzyme that oxidizes cholesterol using is_associated_with::molecular is_associated_with::oxygen.

It is is_associated_with::downregulated by is_associated_with::Sterol regulatory element-binding proteins (SREBP) when plasma cholesterol levels are low. It is upregulated by the nuclear receptor LXR (liver X receptor) when cholesterol (to be specific, oxysterol) levels are high.

The effect of this upregulation is to increase the production of bile acids and reduce the level of cholesterol in hepatocytes.

Clinical significance
Deficiency of this enzyme will increase the possibility of cholesterol gallstones.