catalytic activity:Cholest-5-ene-3-beta,25-diol + NADPH + O(2) = cholest-5-ene-3-beta,7-alpha,25-triol + NADP(+) + H(2)O.,catalytic activity:Cholest-5-ene-3-beta,27-diol + NADPH + O(2) = cholest-5-ene-3-beta,7-alpha,27-triol + NADP(+) + H(2)O.,cofactor:Heme group.,disease:Defects in CYP7B1 are the cause of congenital bile acid synthesis defect type 3 (CBAS3) [MIM:603711]. Clinical features include severe cholestasis, cirrhosis and liver synthetic failure. Hepatic microsomal oxysterol 7-alpha-hydroxylase activity is undetectable.,disease:Defects in CYP7B1 are the cause of spastic paraplegia autosomal recessive type 5A (SPG5A) [MIM:270800]. Spastic paraplegia is a neurodegenerative disorder characterized by a slow, gradual, progressive weakness and spasticity of the lower limbs. Rate of progression and the severity of symptoms are quite variable. Initial symptoms may include difficulty with balance, weakness and stiffness in the legs, muscle spasms, and dragging the toes when walking. In some forms of the disorder, bladder symptoms (such as incontinence) may appear, or the weakness and stiffness may spread to other parts of the body.,pathway:Lipid metabolism; bile acid biosynthesis.,similarity:Belongs to the cytochrome P450 family.,tissue specificity:Brain, testis, ovary, prostate, liver, colon, kidney, and small intestine.,
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