11β-hydroxylase

Enzyme involved in steroid biosynthesis

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Structure of 11β-hydroxylase

Identifiers
EC number	1.14.15.4
CAS number	9015-71-8
Alt. names
IntEnz	IntEnz view
BRENDA	BRENDA entry
ExPASy	NiceZyme view
KEGG	KEGG entry
MetaCyc	metabolic pathway

11β-hydroxylase is an enzyme that plays a crucial role in the biosynthesis of glucocorticoids and mineralocorticoids, which are essential hormones produced in the adrenal cortex. This enzyme is encoded by the CYP11B1 gene and is part of the cytochrome P450 superfamily.

Function

11β-hydroxylase catalyzes the conversion of 11-deoxycortisol to cortisol and 11-deoxycorticosterone to corticosterone. These reactions are critical steps in the steroidogenesis pathway, which is responsible for the production of steroid hormones. The enzyme requires molecular oxygen and NADPH as cofactors to carry out these hydroxylation reactions.

Clinical significance

Mutations in the CYP11B1 gene can lead to a condition known as Congenital adrenal hyperplasia due to 11β-hydroxylase deficiency. This disorder is characterized by an overproduction of androgens and a deficiency in cortisol and aldosterone, leading to symptoms such as hypertension, virilization, and electrolyte imbalance.

Regulation

The activity of 11β-hydroxylase is regulated by the adrenocorticotropic hormone (ACTH), which stimulates the adrenal cortex to produce cortisol. Feedback mechanisms involving cortisol levels help maintain homeostasis in the body.

Structure

11β-hydroxylase is a membrane-bound enzyme located in the mitochondria of adrenal cortex cells. It is composed of a heme group that facilitates the transfer of electrons necessary for the hydroxylation process.

Pathway

The enzyme is part of the steroidogenesis pathway, which includes several other enzymes such as 21-hydroxylase and 17α-hydroxylase. These enzymes work in concert to produce various steroid hormones from cholesterol.

Also see

• Steroidogenesis
• Congenital adrenal hyperplasia
• Cortisol
• Cytochrome P450