11β-Hydroxysteroid dehydrogenase type 1: Purification from human liver and characterization as carbonyl reductase of xenobiotics

11β-Hydroxysteroid dehydrogenase type 1 (11β-HSD1) catalyzes the interconversion of 11-oxo glucocorticoids to their 11-hydroxy metabolites, thereby controlling access of glucocorticoid hormones to the glucocorticoid receptor. Interestingly, evidence is emerging that 11β-HSD1 fulfills an additional role in the metabolism of xenobiotic carbonyl compounds. In our studies, 11β-HSD1 was identified as a microsomal reductase that initiates the final detoxification of xenobiotics by reducing them to alcohols that are easier to conjugate and eliminate. With its pluripotent substrate specificities for glucocorticoids and xenobiotics, 11β-HSD1 adds to an expanding list of those hydroxysteroid dehydrogenases which, on the one hand, are capable of catalyzing the carbonyl reduction of non-steroidal carbonyl compounds, and which, on the other hand, exhibit great specificity to their physiological steroid substrates. It is conceivable that large interferences must occur between endogenous steroid metabolism and the detoxification of xenobiotic compounds on the level of hydroxysteroid dehydrogenases.