Abstract
Abscisic acid (ABA) is an essential mediator in triggering plant responses to environmental stresses. Biosynthesis, transportation, and catabolism of ABA have to be appropriately controlled in order to produce adaptive responses to the stresses. The major catabolic inactivation of ABA is initiated by the 8'-hydroxylation. The specific inhibitors of ABA 8'-hydroxylase are very useful tools for investigation in the field of plant physiology. If the P450 inhibitor is designed regardless of the structure of native substrate, its specificity is not defined unless it is screened for all the enzymes from some hundreds of P450 genes in plants. Therefore, the specific inhibitors of ABA 8'-hydroxylase should be designed based on the substrate specificity. We have examined 45 analogs for detailed substrate specificity for this enzyme. We will discuss a difference between substrate specificity for ABA 8'-hydroxylase and structural requirement for ABA activity, for designing the specific inhibitor of ABA 8'-hydroxylase.
