2001 Fiscal Year Final Research Report Summary
Functions and reaction mechanisms of cytochrome P450 in the biosynthesis of plant constituents
| Project/Area Number |
12680596
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Bioorganic chemistry
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| Research Institution | Gifu Pharmaceutical University |
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Principal Investigator |
INOUE Kenichiro Gifu Pharmaceutical University・Faculty of Pharmaceutical Sciences, Professor, 薬学部, 教授 (40025713)
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| Co-Investigator(Kenkyū-buntansha) |
HAYASHI Hiroaki Gifu Pharmaceutical University ・Faculty of Pharmaceutical Sciences, Assistant, 薬学部, 助手 (50260998)
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| Project Period (FY) |
2000 – 2001
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| Keywords | cytochrome P450 / 7-deoxyloganin hydroxylase / cornoside synthase / iridoid glucoside / gecologanin / cornoside / biosynthesis / cultured cell |
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| Research Abstract |
The aim of this research is to reveal functions and reaction mechanisms of cytochrome P450 in the biosynthesis of plant constituents, in particular monoterpene (iridoid) and benzoquinol glucosides.
Biosynthesis of iridoid glucosides was known to comprise many oxidative processes, indicative of the most suitable for investigating cytochrome P450 responsible for biosynthesis of plant constituents.
Our biosynthetic research using Lonicera japonica cultured cells established that secologanin synthase, which catalyzed the oxidative ring cleavage of loganin, and 7-hydroxylase of 7-deoxyloganin leading to loganin were both cytochrome P450 monooxygenases and proposed the mechanisms for their reactions. On the basis of further investigations such as substrate specificity and kinetic analysis of DLHase as well as the properties of methyl transferase and glucosyl transferase, DLHase adopted 7-deoxyloganin as the most specific substrate but 7-deoxyloganic acid as a sole substrate in secologanin biosynthesis in the cells. These results support the pathway from 7-deoxyloganetic acid via 7-deoxyloganic acid, loganic acid and loganin leading to secologanin. In addition, 7-deoxyloganetic acid and the precursors before it were chemically synthesized except for 11-hydroxyiridodial (easily isomerizable) and the enzymic experiments with them are in progress.
We also established that the oxidation enzyme associated with the formation of cornoside, a unique benzoquinol glucoside is a P450 monooxygenase in the cultured cells of Abeliophyllum distichum and proposed its mechanism.
The above results show the diversity of functions and mechanisms of cytochrome P450 enzymes related to the biosynthesis of plants constituents.
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