Involvement of a 3 β-hydroxysteroid dehydrogenase activity in ecdysteroid biosynthesis

• Published in: Molecular and cellular endocrinology 1997-04, Vol.128 (1), p.139-149
• Main Authors: Dauphin-Villemant, C, Böcking, D, Blais, C, Toullec, J-Y, Lafont, R
• Format: Article
• Language: English
• Subjects: 3 β-hydroxysteroid dehydrogenase; 3-keto-reductase; Ecdysteroids (Crustaceans); Molting glands; Steroidogenesis
• ISSN: 0303-7207; 1872-8057
• DOI: 10.1016/S0303-7207(97)04031-8

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 5 β-ketodiol (2,22,25-trideoxyecdysone), 2,22deoxyecdysone and 2-deoxyecdysone but not from E. Further experiments were performed in order to understand the interconversions between 3-oxo and 3 β-OH compounds in the crab Y-organ. The enzyme involved in 3 β-dehydrogenation was not ecdysone oxidase, a soluble enzyme found in peripheral tissues of many arthropods but it presented strong similarities with 3 β-hydroxysteroiddehydrogenase enzymes from vertebrates: it was membrane-bound and NAD +-dependent. Moreover, a NADH-dependent 3 β-reduction of several 3-oxo-ecdysteroids was obtained using the same microsomal fraction (100 000× 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 3 β-hydroxysteroid dehydrogenase enzyme involved in the biosynthetic pathway of ecdysteroids.