数種の植物成分の生合成におけるシトクロムp450酸化酵素の反応と機能

Abstract

Secologanin, a secoiridoid glucoside, is a pivotal terpenoid intermediate in the biosynthesis of biologically active monoterpenoid indole alkaloids such as reserpine, ajmaline, and vinblastine which are biosynthesized via strictosidine, an alkaloidal glucoside, formed from secologanin and tryptamine. In secologanin biosynthesis, the oxidative cleavage process of loganin to secologanin and the hydroxylation of 7-deoxyloganin to loganin have remained unknown enzymologically and mechanistically. Cornoside is a unique glucoside with 4-hydroxy-2,5-cyclohexadien-1-one (benzoquinol) ring and is widespread in families such as Cornaceae, Oleaceae, and Scrophulariaceae but its biosynthesis, especially the oxidative process, remain to be investigated. Shikonin is a red naphthazarin pigment derived from the roots of Lithospermum erythorhizon and produced biotechnologically by cell cultures. Its biosynthesis including the production regulation mechanism has been investigated in detail. However, the naphthazarin ring formation process, probably starting with the hydroxylation of the side chain of geranylhydroquinone, a key intermediate at the late stage of shikonin biosynthesis, remained unknown. In the present review, cytochrome P450 monooxygenases involved in the biosyntheses of three structurally and biosynthetically interesting compounds, secologanin, cornoside, and shikonin, a described together with the results of previous and recent biosynthetic studies. The biosyntheses of related compounds are also discussed.

Expression, crystallization and preliminary X-ray analysis of McbB, a multifunctional enzyme involved in β-carboline skeleton biosynthesis

“…Secologanin synthase, an NADPH-dependent P450 oxidase, is used to catalyse the oxidative cleavage of loganin to generate secologanin (Irmler et al, 2000). Similar to secologanin synthase, it has been discovered that cytochrome P450 monooxygenases are involved in the biosynthesis of secologanin, cornoside and shikonin (Inoue, 2005). Another reaction frequently detected in the biosynthesis of alkaloids is decarboxylation.…”