title: Abscinazole-E2B, a practical and selective inhibitor of ABA 8'-hydroxylase CYP707A.
abstract: We developed abscinazole-E2B (Abz-E2B), a practical and specific inhibitor of abscisic acid (ABA) 8'-hydroxylase (CYP707A), by structural modification of abscinazole-E1 (Abz-E1), another compound we developed. A butoxy group was introduced to Abz-E2B instead of the tosylate group of Abz-E1, in expectation of better water solubility, because the calculated logP value of Abz-E2B is 3.47, which is smaller than that of Abz-E1 (4.02). The water solubility of Abz-E2B was greater than 90% at a concentration of 100 μM, at which the solubility of Abz-E1 was 20%. The enzyme specificity was improved significantly. In in vitro assays constructed using recombinant enzymes, (±)-Abz-E2B was a considerably weaker inhibitor than (±)-Abz-E1 for CYP701A, a GA biosynthetic enzyme, which is a target of S-uniconazole (S-UNI), a lead compound of Abz-E1. (±)-Abz-E2B application to plants resulted in improved desiccation tolerance and an increase in endogenous ABA, with little retardation of growth. We also prepared optically pure Abz-E2B and determined its absolute configuration. The R-enantiomer of Abz-E2B was the more potent inhibitor of CYP707A, unlike UNI, whereas both enantiomers were markedly less effective than S-UNI in inhibiting CYP701A. Because S-Abz-E2B arrested the growth of rice seedlings at 100 μM, probably because of off-target effects, R-Abz-E2B should be used as a chemical tool for research focusing on CYP707A when 100 μM or higher concentration is required, although (±)-Abz-E2B may be useful as an alternative option at a lower concentration.
authors.affiliation: Department of Applied Biological Chemistry, Faculty of Agriculture, Shizuoka University, Shizuoka 422-8529, Japan.
authors.forename: Mariko
authors.initials: M
authors.lastname: Okazaki
authors.forename: Monrudee
authors.initials: M
authors.lastname: Kittikorn
authors.forename: Kotomi
authors.initials: K
authors.lastname: Ueno
authors.forename: Masaharu
authors.initials: M
authors.lastname: Mizutani
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Hirai
authors.forename: Satoru
authors.initials: S
authors.lastname: Kondo
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Ohnishi
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Todoroki
mesh_terms: D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology; D015394:Molecular Structure; D012275:Oryza / Q000187:drug effects* / Q000254:growth & development; D010940:Plant Proteins; D036226:Seedlings / Q000187:drug effects; D012995:Solubility; D013379:Substrate Specificity; D014230:Triazoles / Q000737:chemistry* / Q000494:pharmacology*; D014867:Water / Q000737:chemistry
chemical_list: D065607:Cytochrome P-450 Enzyme Inhibitors; D004791:Enzyme Inhibitors; D010940:Plant Proteins; D014230:Triazoles; C574130:abscinazole-E2B; D014867:Water; D003577:Cytochrome P-450 Enzyme System; C107203:abscisic acid 8'-hydroxylase