CYP7B1: Proteins and Enzymes

P450 enzymes constitute a family of monooxygenase enzymes that are involved in the metabolism of a wide array of endogenous and xenobiotic compounds including cholesterol. CYP8B1 moderates the ratio of cholic acid over chenodeoxycholic acid to control the solubility of cholesterol. P450 cholesterol 7-hydroxylase, CYP7A1, is the rate limiting enzyme of bile acid synthesis in the liver, and its expression is mediated by the bile acid receptor FXR. CYP27A1 catalyzes vitamin D3 25-hydroxylation and is localized to the mitochondria in kidney and liver. CYP7B1 (oxysterol 7-alpha-hydroxylase) functions as an enzyme in the alternate bile acid synthesis pathway. Specifically, CYP7B1 metabolizes 25- and 27-hydroxycholesterol. The gene encoding human CYP7B1 maps to chromosome 8q21.3. Mutations in the CYP7B1 gene may cause a metabolic defect in bile acid synthesis characterized by elevated urinary bile acid excretion, severe cholestasis, cirrhosis and liver synthetic failure.