Steroid 21-Hydroxylase

**Definition:** An adrenal microsomal cytochrome P450 enzyme that catalyzes the 21-hydroxylation of steroids in the presence of molecular oxygen and NADPH-FERRIHEMOPROTEIN REDUCTASE. This enzyme, encoded by CYP21 gene, converts progesterones to precursors of adrenal steroid hormones (CORTICOSTERONE; HYDROCORTISONE). Defects in CYP21 cause congenital adrenal hyperplasia (ADRENAL HYPERPLASIA, CONGENITAL).

**Tree numbers:** - D08.244.453.493.500 - D08.244.453.915.760 - D08.811.682.690.708.170.463.500 - D08.811.682.690.708.170.915.760 - D12.776.422.220.453.493.500 - D12.776.422.220.453.915.760

**Synonyms:** - Cytochrome P-450 21-Hydroxylase - Cytochrome P-450(c-21) - Progesterone 21-Hydroxylase - Steroid-21-Hydroxylase - Steroid 21-Monooxygenase - Cytochrome P450c21 - Cytochrome P-450 c21 - 21-Hydroxylase - Cytochrome P-450 CYP21