14. シロイヌナズナCYP90B1はC27, C28, C29ブラシノステロイドのC-22位を水酸化する

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Arabidopsis dwf4 is a brassinosteroid deficient mutant, and the DWF4 gene has been reported to encode a cytochrome P450, CYP90B1. Here, we report the catalytic activity and substrate specificity of the CYP90B1 protein. The recombinant CYP90B1 was produced in E. coli. The measurement of type I substrate binding spectra of CYP90B1 demonstrated that sterols showed 10 times stronger affinity to the P450 than the corresponding stanols. CYP90B1 activity was measured in an assay reconstituted with NADPH-P450 reductase, and the reaction products were analyzed by GC-MS. The recombinant CYP90B1 catalyzed the C-22 hydroxylation of campestanol to produce 6-deoxocathasterone. Substrate specificity of the CYP90B1 revealed that campesterol was much better substrate than campestanol, suggesting that the early C-22 hydroxylation pathway is a main route in the BR biosynthetic pathway. In addition, CYP90B1 showed the C-22 hydroxylation activity toward various C_<27>, C_<28>, and C_<29> sterols, indicating that CYP90B1 functions in the biosynthesis of C_<27>, C_<28>, and C_<29> brassinosteroids. To our knowledge, this is the first report of the biochemical evidence for the C-22 hydroxylation by the P450.
植物化学調節学会の論文
2004-10-13