21-Hydroxylase

Steroid 21-is_associated_with::hydroxylase is a is_associated_with::cytochrome P450 is_associated_with::enzyme that is involved with the is_associated_with::biosynthesis of the is_associated_with::steroid hormones is_associated_with::aldosterone and is_associated_with::cortisol.

In humans, 21-Hydroxylase is encoded by the is_associated_with::gene CYP21A2.

Function
This gene encodes a member of the is_associated_with::cytochrome P450 superfamily of enzymes. The is_associated_with::cytochrome P450 proteins are is_associated_with::monooxygenases which catalyze many reactions involved in drug metabolism and synthesis of is_associated_with::cholesterol, is_associated_with::steroids and other is_associated_with::lipids. This protein localizes to the is_associated_with::endoplasmic reticulum and hydroxylates steroids at the 21 position. Its activity is required for the synthesis of steroid hormones including is_associated_with::cortisol and is_associated_with::aldosterone.

Clinical significance
A defect within the is_associated_with::CYP21A2 gene causes a disturbance of the development of the enzyme, which leads to is_associated_with::congenital adrenal hyperplasia due to 21-hydroxylase deficiency. A related is_associated_with::pseudogene is located near this gene; is_associated_with::gene conversion events involving the functional gene and the pseudogene are thought account for many cases of steroid 21-hydroxylase deficiency.

Names and classification
21-Hydroxylase is also called steroid 21-monooxygenase, 21α-Hydroxylase, and, less commonly 21β-Hydroxylase.

Reaction
21-Hydroxylase catalyses the is_associated_with::hydroxylation of the is_associated_with::carbon atom 21 in is_associated_with::steroids (adding an "–OH"), which is necessary with the formation of these is_associated_with::hormones.