title: 5Alpha-androstane-3beta,7alpha,17beta-triol and 5alpha-androstane-3beta,7beta,17beta-triol as substrates for the human 11beta-hydroxysteroid dehydrogenase type 1.
abstract: Several studies have shown that the native 7alpha-hydroxy-dehydroepiandrosterone (7alpha-hydroxy-DHEA) is a substrate for the human 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) which converts the 7alpha- into the 7beta-epimer through an oxido-reduction process. Research on the 11beta-HSD1 has investigated its function and structure through using native glucocorticoid substrates and known inhibitors. Other steroid substrates are also of interest. Among testosterone metabolites, 5alpha-androstane-3beta,17beta-diol (Adiol) is a substrate for the cytochrome P450 7B1 which produces 5alpha-androstane-3beta,7alpha,17beta-triol (7alpha-Adiol). This steroid may be a substrate for the 11beta-HSD1. We used recombinant yeast-expressed 11beta-HSD1 with NADP(H)-regenerating systems for examining the products obtained after incubation with 7alpha-Adiol, 7beta-Adiol or 7-oxo-Adiol. Oxidative conditions for the 11beta-HSD1 provided no trace of 7-oxo-Adiol but the inter-conversion of 7alpha- and 7beta-hydroxy-Adiol with V(max)/K(M) (pmol min(-1) microg(-1)/microM) values of 2 and 0.5, respectively. This state was maintained under reductive conditions. The use of a 7-oxo-Adiol substrate under reductive conditions led to the production of both 7alpha- and 7beta-hydroxy-Adiol with V(max)/K(M) values of 3.43 and 0.22, respectively. These findings support the hypothesis that the oxido-reductase and epimerase activities of 11beta-HSD1 depend on the positioning of the steroid substrates within the active site and may provide insight into its fine structure and mechanism of action.
authors.affiliation: Chaire de Génie Biologique, EA-3199, Conservatoire National des Arts et Métiers, 2 rue Conté, 75003 Paris, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Hennebert
authors.forename: Sandrine
authors.initials: S
authors.lastname: Le Mée
authors.forename: Christine
authors.initials: C
authors.lastname: Pernelle
authors.forename: Robert
authors.initials: R
authors.lastname: Morfin
mesh_terms: D043205:11-beta-Hydroxysteroid Dehydrogenase Type 1 / Q000737:chemistry*; D015113:Androstane-3,17-diol / Q000031:analogs & derivatives* / Q000737:chemistry; D006801:Humans; D007700:Kinetics; D013379:Substrate Specificity; D014867:Water / Q000737:chemistry