US EPA

7066752 

Journal Article 

Abscinazole-E2B, a practical and selective inhibitor of ABA 8 '-hydroxylase CYP707A 

Okazaki, M; Kittikorn, M; Ueno, K; Mizutani, M; Hirai, N; Kondo, S; Ohnishi, T; Todoroki, Y; , 

2012 

Yes 

Bioorganic & Medicinal Chemistry
ISSN: 0968-0896
EISSN: 1464-3391 

PERGAMON-ELSEVIER SCIENCE LTD 

OXFORD 

3162-3172 

22525496 

10.1016/j.bmc.2012.03.068 

WOS:000303530900002 

We developed abscinazole-E2B (Abz-E2B), a practical and specific inhibitor of abscisic acid (ABA) 80hydroxylase (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 log P 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 mu M, 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 mu M, probably because of off-target effects, R-Abz-E2B should be used as a chemical tool for research focusing on CYP707A when 100 mu M or higher concentration is required, although (+/-)-Abz-E2B may be useful as an alternative option at a lower concentration. (C) 2012 Elsevier Ltd. All rights reserved.