Steroid 11-beta-hydroxylase

Steroid 11β-hydroxylase is a is_associated_with::steroid hydroxylase found in the is_associated_with::zona glomerulosa and is_associated_with::zona fasciculata. Named officially the cytochrome P450 11B1, mitochondrial, it is a is_associated_with::protein that in humans is encoded by the CYP11B1 is_associated_with::gene.

This gene encodes a member of the is_associated_with::cytochrome P450 superfamily of is_associated_with::enzymes. The cytochrome P450 proteins are monooxygenases that catalyze many reactions involved in drug metabolism and synthesis of is_associated_with::cholesterol, is_associated_with::steroids and other lipids. This protein localizes to the mitochondrial inner membrane and is involved in the conversion of 11-deoxycortisol to cortisol in the adrenal cortex. Transcript variants encoding different isoforms have been noted for this is_associated_with::gene.

It is reversibly inhibited by is_associated_with::etomidate and is_associated_with::metyrapone.

Function
It generates is_associated_with::cortisol from is_associated_with::11-deoxycortisol and is_associated_with::corticosterone from 11-is_associated_with::deoxycorticosterone. Note the extra "–OH" added at the 11 position (near the center, on ring "C"):

Mechanism of action
As a mitochondrial P450 system, P450c11 is dependent on two electron transfer proteins, adrenodoxin reductase and adrenodoxin that transfer 2 electrons from NADPH to the P450 for each monooxygenase reaction catalyzed by the enzyme. In most respects this process of electron transfer appears similar to that of is_associated_with::P450scc system that catalyzes cholesterol side chain cleavage. Similar to P450scc the process of electrons transfer is leaky leading to superoxide production. The rate of electron leakage during metabolism depends on the functional groups of the steroid substrate.

Regulation
The expression of the enzyme in adrenocortical cells is regulated by the trophic hormone corticotropin (is_associated_with::ACTH.

Clinical significance
A mutation is associated with is_associated_with::congenital adrenal hyperplasia due to 11β-hydroxylase deficiency.