RESUMEN
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.
Asunto(s)
Inhibidores Enzimáticos del Citocromo P-450 , Oryza/efectos de los fármacos , Triazoles/química , Triazoles/farmacología , Sistema Enzimático del Citocromo P-450 , Inhibidores Enzimáticos/química , Inhibidores Enzimáticos/farmacología , Estructura Molecular , Oryza/crecimiento & desarrollo , Proteínas de Plantas , Plantones/efectos de los fármacos , Solubilidad , Especificidad por Sustrato , Agua/químicaRESUMEN
We developed abscinazole-E1 (Abz-E1), a specific inhibitor of abscisic acid (ABA) 8'-hydroxylase (CYP707A). This inhibitor was designed and synthesized as an enlarged analogue of uniconazole (UNI), a well-known plant growth retardant, which inhibits a gibberellin biosynthetic enzyme (ent-kaurene oxidase, CYP701A) as well as CYP707A. Our results showed that Abz-E1 functions as a potent inhibitor of CYP707A and a poor inhibitor of CYP701A both in vitro and in vivo. Abz-E1 application to plants resulted in improved desiccation tolerance and an increase in endogenous ABA.
