title: Characterization of three hydroxylases involved in the final steps of biosynthesis of the steroid hormone ecdysone in Locusta migratoria (Insecta, Orthoptera).
abstract: It is most generally accepted that the last three enzymatic reactions in the biosynthetic pathway of ecdysone are, in this order, the hydroxylations at positions C-25, C-22 and C-2. Using high specific activity tritiated ecdysone precursors (2,22,25-trideoxyecdysone, 2,22-dideoxyecdysone and 2-deoxyecdysone) we have characterized the hydroxylases involved in these reactions, in the major biosynthetic tissue of ecdysone, i.e. the prothoracic glands. We show that C-2 hydroxylase is a mitochondrial oxygenase which differs from conventional cytochrome P-450-dependent monooxygenases by its relative insensitivity to CO. In contrast, C-22 and C-25 hydroxylases appear as classical cytochrome P-450 monooxygenases; C-22 hydroxylase is a mitochondrial enzyme whereas our data point to a microsomal localization of the C-25 hydroxylase.
authors.affiliation: Unité Associée au CNRS 672, l'Université Louis Pasteur, Strasbourg, France.
authors.forename: C
authors.initials: C
authors.lastname: Kappler
authors.forename: M
authors.initials: M
authors.lastname: Kabbouh
authors.forename: C
authors.initials: C
authors.lastname: Hetru
authors.forename: F
authors.initials: F
authors.lastname: Durst
authors.forename: J A
authors.initials: JA
authors.lastname: Hoffmann
mesh_terms: D000818:Animals; D004440:Ecdysone / Q000096:biosynthesis*; D006110:Grasshoppers / Q000378:metabolism*; D007700:Kinetics; D006899:Mixed Function Oxygenases / Q000378:metabolism*; D008954:Models, Biological; D009243:NAD / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism
chemical_list: D009243:NAD; D004440:Ecdysone; D009249:NADP; D006899:Mixed Function Oxygenases