44.アブシジン酸8'-水酸化酵素リガンドの基本構造(口頭発表)

概要

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ABA 8'-hydroxylase (recombinant CYP707A3) active site specifically binds (S)-(+)-ABA, naturally occurring ABA, but not its enantiomer (R)-(-)-ABA. On the other hand, enone-lacking (-)-ABA analogs (e.g. (-)-4'-deoxo-ABA and (-)-AHI1) bind to the enzyme, indicating that the ketone in the ring of (-)-ABA prevents binding to the enzyme due to decrease of the lipophilicity or unfavorable electrostatic interaction with the active site. This hypothesis has led us to speculate that an ABA analog with the same side chain as that of ABA can bind to the CYP707A3 active site independent of its C1'-configuration if its six-membered ring has no oxygenated functional group except for the C1'-hydroxyl group. Therefore, we tested the epimer of AHI1 (epi-ARI1), AHI1 analogs which are lacking the methyl group(s) in the ring (C8' and C9'), β-ionylideneacetic acid and phenylpentadienoic acid. These compounds except for phenylpentadienoic acid inhibited the enzyme reaction, thus supporting our speculation. Notably, 6-hydroxy-6-isopropyl-7-methyloctadienoic acid, a ring-opened compound, also exhibited enzyme inhibitory activity, whereas 7,7,7-trifluoro-6-hydroxy-6-methylheptadienoic acid cannot bind to the active site. These results suggest that 2Z,4E-pentadienoic acid can bind to ABA 8'-hydroxylase if it has a branched C7 hydrocarbon, which is accommodated by the hydrophobic binding pocket, at the C-5 position.
植物化学調節学会の論文
2007-10-05