25-hydroxycholesterol 7alpha-hydroxylase (EC 1.14.13.100 25-hydroxycholesterol 7alpha-monooxygenase CYP7B1 CYP7B1 oxysterol 7alpha-hydroxylase) is an enzyme with system name cholest-5-ene-3beta25-diolNADPH:oxygen oxidoreductase (7alpha-hydroxylating).