A-6 3'-フルオロアブシジン酸代謝物の生理活性

概要

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ABA(1)is metabolized to 8'-hydroxy-ABA(2) which isomerizes to phaseic acid(3), and 3 is reduced to dihydrophaseic acid(4). The activity of 3 is lower than 1, and 4 is almost inactive. However, the activity of 2 is unknown since 2 is spontaneously isomerizes to 3 in vitro. In order to estimate the activity of 2 we tested the biological activities of 3'-fluoro-8'-hydroxy-ABA(6), a stable metabolite of 3'-fluoro-ABA(5). Compound 6 was obtained by feeding 5 to suspension culture of rice cells. Compound 6 was stable at pH2-6 although it isomerized rapidly to 3'a-fluorophaseic acid(7)at pH 8-10. Inhibitory activity of 6 was lower than 5, and higher than 7 in assays of lettuce seed germination, rice seedling elongation and stomata opening. The lower activity of 6 could be caused by hydrophilicity of the 8'-hydroxyl group since the C-8' and -9' of 1 seem to interact with a hydrophobic domain of ABA-binding proteins. This result strongly suggests that the activity of 2 is lower than 1. And higher than 3. Therefore, 1would be inactivated stepwise by metabolic enzymes, 8'-hydroxylase, 8'-hydroxy-ABA cyclase, and phaseic acid reductase, in plants.
植物化学調節学会の論文
1998-10-01