Multifunctionality of human 17β-hydroxysteroid dehydrogenases

17 beta-Hydroxysteroid dehydrogenases (17 beta-HSDs) belong to the family of short chain dehydrogenases/reductases (SDRs) and aldoketo-reductases (AKRs). Some of the enzymes were discovered and named due to their enzymatic activity on steroid substrates or according to their sequence homology to other 17 beta-HSDs. During characterisation of these enzymes it turned out that their substrate specificity is broader than first expected and key functions of some 17 beta-HSDs in vivo are probably not in steroid metabolism but in basic metabolic pathways. The issue of such multifunctionality is the topic of this review. (c) 2005 Elsevier Ireland Ltd. All rights reserved.