101 アブシジン酸(ABA)代謝酵素、ABA-oxygenaseの立体選択性(ポスター発表の部)

概要

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Differences in catabolism of the enantiomers of abscisic acid (ABA) have been reported. Natural (+)-S-ABA is metabolized rapidly via two major pathways. One route involves the conjugation with glucose to form ABA glucose ester. A second pathway consists of oxidation of ABA by ABA oxygenase, the enzyme that forms 8'-hydroxyABA from ABA, to phaseic and dihydrophaseic acid (PA and DPA). The R-enantiomer metabolized slowly to the conjugates and 7'-hydroxy-(-)-R-ABA but not to PA or DPA. These results indicate that the stereoselectivity of ABA oxygenase is thought to be strict. However, no rigorous evidence has been obtained so far, because there were no analytical methods to establish the optical purity of PA and DPA. Recently we have achieved the direct optical resolution of PA and DPA by HPLC on the chiral stationary phase. To examine the stereoselectivity of ABA oxygenase, the PA and DPA isolated after feeding of (±)-RS-[^2H_6]-ABA to avocado mesocarp were analysed by the chiral HPLC methods. The peaks of unnatural PA and DPA arising from the unnatural enantiomer of ABA could be observed. These results show that the stereoselectivity of ABA oxygenase is not so strict under our experimental conditions.
天然有機化合物討論会の論文
1992-09-10