55. ABA 8'-水酸化酵素におけるABA不斉認識に必要な官能基

概要

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The plant hormone (1'S)-(+)-ABA is inactivated through 8'-hydroxylation by ABA 8'-hydroxylase (Arabidopsis CYP707A3), whereas (1'R)-(-)-ABA does not bind to the enzyme. (1'S,2'S)-(+)-6-Nor-2',3'-dihydro-4'-deoxo-ABA [(+)-1], which we developed as a lead compound for inhibitors of ABA 8'-hydroxylase, functioned as an enzyme substrate. The lead (-)-1 was not a substrate of the enzyme, however, the inhibitory activity of (-)-1 on 8'-hydroxylation of ABA was higher than that of (+)-1. The result suggests that the enone of cyclohexenone ring is the key to chiral recognition by ABA 8'-hydroxylase. Thus, we planned to synthesize 2',3'-dihydro-ABA and 4'-deoxo-ABA and test these compounds for the inhibition in the ABA 8'-hydroxylase reaction to investigate the phenomena in detail. (1'S,2'S)-(+)-2',3'-dihydro-ABA slightly inhibited the CYP707A3 reaction, whereas (1'R,2'R)-(-)-2',3'-dihydro-ABA did not bind to the enzyme as well as (-)-ABA. The observation indicates the importance of the carbonyl group at C-4' for chiral recognition by ABA 8'-hydroxylase. We are preparing 4'-deoxo-ABA and measuring its inhibitory activity on ABA 8'-hydroxylase reaction at present.
2005-10-13