What is the Origin of 11β-Hydroxysteroid Dehydrogenase Type 2?

The term is derived from its chemical function and its location within the body's steroid metabolism pathways. "11β-Hydroxysteroid Dehydrogenase" indicates the enzyme's action on the hydroxyl group at the eleventh carbon position of the steroid ring. The designation "Type 2" distinguishes it from its counterpart, Type 1, based on its specific direction of reaction and its tissue distribution. This enzyme is predominantly expressed in mineralocorticoid-responsive tissues, such as the kidney, colon, and salivary glands.

What is the Mechanism of 11β-Hydroxysteroid Dehydrogenase Type 2?

The enzyme operates by utilizing the cofactor NAD+ to catalyze the oxidation of the 11-hydroxyl group on cortisol, resulting in the formation of 11-ketocortisone, known as cortisone. This reaction effectively inactivates cortisol, preventing it from binding to the mineralocorticoid receptor with high affinity. This protective mechanism ensures that aldosterone, the primary mineralocorticoid, can exert its effects on sodium and potassium balance without interference from cortisol. Dysfunction in this enzyme's activity can lead to a state of functional mineralocorticoid excess, impacting blood pressure and fluid regulation.

11β-Hydroxysteroid Dehydrogenase Type 2

Meaning

This enzyme, abbreviated as 11β-HSD2, is a critical component of the body’s mineralocorticoid system, primarily responsible for regulating the balance between active and inactive corticosteroids. It functions as a dehydrogenase, specifically converting the potent glucocorticoid cortisol into its inactive metabolite, cortisone. This precise metabolic action is vital for protecting the mineralocorticoid receptor from being inappropriately activated by the high local concentrations of cortisol. Its clinical significance lies in its role in maintaining electrolyte homeostasis and preventing conditions like apparent mineralocorticoid excess syndrome.