title: Involvement of a 3beta-hydroxysteroid dehydrogenase activity in ecdysteroid biosynthesis.
abstract: Ecdysteroid biosynthesis was analyzed in vitro using dissociated Y-organ cells from the shore crab Carcinus maenas. 3-Dehydroecdysone (3DE) was detected as a minor secretory product, in addition to the formerly identified end-products 25-deoxyecdysone and ecdysone (E). In conversion studies, 3DE was formed from tritiated 5beta-ketodiol (2,22,25-trideoxyecdysone), 2,22-deoxyecdysone and 2-deoxyecdysone but not from E. Further experiments were performed in order to understand the interconversions between 3-oxo and 3beta-OH compounds in the crab Y-organ. The enzyme involved in 3beta-dehydrogenation was not ecdysone oxidase, a soluble enzyme found in peripheral tissues of many arthropods but it presented strong similarities with 3beta-hydroxysteroid dehydrogenase enzymes from vertebrates: it was membrane-bound and NAD+-dependent. Moreover, a NADH-dependent 3beta-reduction of several 3-oxo-ecdysteroids was obtained using the same microsomal fraction (100,000 x g pellet) of Y-organs, indicating that the reaction might be reversible. As this activity was specific of molting glands, we hypothesize that there is at least one 3beta-hydroxysteroid dehydrogenase enzyme involved in the biosynthetic pathway of ecdysteroids.
authors.affiliation: Ecole Normale Supérieure, Département de Biologie, CNRS EP1 19, Paris, France. villeman@wotwan.ens.fr
authors.forename: C
authors.initials: C
authors.lastname: Dauphin-Villemant
authors.forename: D
authors.initials: D
authors.lastname: Böcking
authors.forename: C
authors.initials: C
authors.lastname: Blais
authors.forename: J Y
authors.initials: JY
authors.lastname: Toullec
authors.forename: R
authors.initials: R
authors.lastname: Lafont
mesh_terms: D015096:3-Hydroxysteroid Dehydrogenases / Q000378:metabolism*; D000818:Animals; D003386:Brachyura; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D026461:Ecdysteroids; D005260:Female; D007700:Kinetics; D008297:Male; D018978:Molting; D009928:Organ Specificity; D013256:Steroids / Q000096:biosynthesis*; D013379:Substrate Specificity
chemical_list: D026461:Ecdysteroids; D013256:Steroids; D015096:3-Hydroxysteroid Dehydrogenases