11β-Hydroxysteroid dehydrogenase (HSD-11β or 11β-HSD) is the name of a family of enzymes that catalyze the conversion of inert 11 keto-products (cortisone) to active cortisol, or vice versa, thus regulating the access of glucocorticoids to the steroid receptors:
11β-hydroxysteroid + NADP+ an 11-oxosteroid + NADPH + H+
This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is 11beta-hydroxysteroid:NADP+ 11-oxidoreductase. Other names in common use include corticosteroid 11beta-dehydrogenase, beta-hydroxysteroid dehydrogenase, 11beta-hydroxy steroid dehydrogenase, corticosteroid 11-reductase, and dehydrogenase, 11beta-hydroxy steroid. This enzyme participates in c21-steroid hormone metabolism and androgen and estrogen metabolism.
Cortisol, a glucocorticoid, binds the glucocorticoid receptor. However, because of its molecular similarity to aldosterone it is also capable of binding the mineralcorticoid receptor. Both aldosterone and cortisol have a similar affinity for the mineralocorticoid receptor; however, there is vastly more cortisol in circulation than aldosterone. To prevent over-stimulation of the mineralocorticoid receptor by cortisol, HSD-11β converts the biologically active cortisol to the inactive cortisone, which can no longer bind to the mineralocorticoid receptor. HSD-11β co-localizes with intracellular adrenal steroid receptors. Licorice or Carbenoxolone, which contains glycyrrhetinic acid, can inhibit 11β-HSD and lead to a mineralocorticoid excess syndrome.
Lakshmi V, Monder C (1988). "Purification and characterization of the corticosteroid 11 beta-dehydrogenase component of the rat liver 11 beta-hydroxysteroid dehydrogenase complex". Endocrinology.123 (5): 2390–8. doi:10.1210/endo-123-5-2390. PMID3139396.