26 イソフラボノイド生合成におけるシトクロムP-450の酸化的芳香環転位反応(口頭発表の部)

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The enzymatic rearrangement in the formation of isoflavone skeleton from flavanone precursor was investigated in elicitor-treated cell suspension cultures of Pueraria lobata Ohwi (Leguminosae). A reaction intermediate formed in the reaction was identified as 2-hydroxyisoflavanone by mass, UV and ^1H NMR spectroscopies. The oxidative aryl migration of flavanone generating 2-hydroxyisoflavanone was catalyzed by a microsomal cytochrome P-450-dependent monooxygenase. The formation of 3-hydroxyflavanone was also observed as a by-product. The dehydration enzyme which catalyzes the conversion of 2-hydroxyisoflavanone into isoflavone was localized in a soluble enzyme fraction. The dehydratase was purified to apparent homogeneity and revealed to be a single polypeptide with a MW of 38 kDa. The treatment of P. lobata cells with yeast extract-elicitor resulted in the induction of the P-450 and the dehydratase, and the treatment of jasmonic acid or methyl jasmonate was also effective. The incorporation experiments using ^<18>O2 gas and ^<18>O-labeled flavanone demonstrated that 2-hydroxyl oxygen of 2-hydroxyisoflavanone was originated from molecular oxygen. Some unnatural flavanones, which lack 4'-hydroxyl function on the side phenyl ring, was also converted into corresponding isoflavones, suggesting that the contribution of spirodienone intermediate involved in the earlier proposals is not essential for the rearrangement reaction. Based on these observations a new mechanism, P-450-mediated hydroxylation associated with migration, was proposed for the oxidative aryl rearrangement.
天然有機化合物討論会の論文
1994-09-20

26 イソフラボノイド生合成におけるシトクロムP-450の酸化的芳香環転位反応(口頭発表の部)

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