title: Rice CYP90D2 and CYP90D3 catalyze C-23 hydroxylation of brassinosteroids in vitro.
abstract: Brassinosteroids are biosynthesized from campesterol via several cytochrome P450 (P450)-catalyzed oxidative reactions. We report the biochemical characterization of two brassinosteroid-biosynthetic P450s from rice: CYP90D2 and CYP90D3. A rice dwarf mutant, ebisu dwarf (d2), which contains a defective copy of CYP90D2, is known to be a brassinosteroid-deficient mutant, and CYP90D2 has been considered to act as a C-3 dehydrogenase. However, in vitro biochemical assays using baculovirus/insect cell-produced proteins revealed that both CYP90D2 and CYP90D3 catalyze C-23 hydroxylation of various 22-hydroxylated brassinosteroids, but with markedly different catalytic efficiencies. Both enzymes preferentially convert (22S,24R)-22-hydroxyergost-4-en-3-one, (22S,24R)-22-hydroxy-5α-ergostan-3-one, and 3-epi-6-deoxocathasterone to the corresponding 23-hydroxylated products, but are less active in the conversion of (22S)-22-hydroxycampesterol and 6-deoxocathasterone, in vitro. Consistently, the levels of 23-hydroxylated products of these intermediates, namely, 6-deoxoteasterone, 3-dehydro-6-deoxoteasterone, and 6-deoxotyphasterol were decreased in d2 mutants. These results indicate that CYP90D2 and CYP90D3 can act as brassinosteroid C-23 hydroxylases in rice.
authors: Faculty of Bioresources and Environmental Sciences, Ishikawa Prefectural University, Nonoichi, Ishikawa 921 8836, Japan. sakamoto@ishikawa-pu.ac.jp
authors: Tomoaki
authors: T
authors: Sakamoto
authors: Toshiyuki
authors: T
authors: Ohnishi
authors: Shozo
authors: S
authors: Fujioka
authors: Bunta
authors: B
authors: Watanabe
authors: Masaharu
authors: M
authors: Mizutani
mesh_terms: D000818:Animals; D016367:Baculoviridae; D060406:Brassinosteroids / Q000378:metabolism*; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D006900:Hydroxylation; D007313:Insecta; D009154:Mutation; D012275:Oryza / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism*; D013250:Steroid Hydroxylases / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D060406:Brassinosteroids; D010940:Plant Proteins; D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases