1988 Fiscal Year Final Research Report Summary
Studies on the biosynthesis of tropane alkaloids by the use of organ cultures.
| Project/Area Number |
62560084
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
応用生物化学・栄養化学
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| Research Institution | Kyoto University |
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Principal Investigator |
HASHIMOTO Takashi Faculty of Agriculture, Kyoto University Instructor, 農学部, 助手 (80180826)
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| Co-Investigator(Kenkyū-buntansha) |
YAMADA Yasuyuki Faculty of Agriculture, Kyoto University Professor, 農学部, 教授 (50026415)
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| Project Period (FY) |
1987 – 1988
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| Keywords | Tropane alkaloids / 6 -Hydroxyhyoscyamine / Scopolamine / Epoxidase / Root culture / 培養茎葉 |
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| Research Abstract |
Hyoscyamine is epoxidized to scopolamine via 6 -hydroxyhyoscyamine (Hyos-OH) in several solanaceous plants. 6,7-Dehydrohyoscyamine has been proposed to be an intermediate in the conversion of Hyos-OH to scopolamine on the basis of the observation that this unsaturated alkaloid is converted to scopolamine when fed to a Datura scion. To determine whether a dehydration step is involved in scopolamine biosynthesis, [6-^<18>O]Hyos-OH was prepared from hyoscyamine and ^<18>O_2 using hyoscyamine 6 -hydroxylase (H6H) obtained from root cultures of Hyoscyamus niger. Similarly, [7 -^2H]Hyos-OH was synthesized from [6 ,7 -^2H_2]hyoscyamine. When these labeled alkaloids were fed to shoot cultures of duboisia myoporoides, [6-^<18>O]Hyos-OH was converted to scopolamine which retained ^<18>O in the epoxide oxygen whereas [7 -^2H]Hyos-OH to scopolamine with no deuterium. It is concluded that Hyos-OH is converted in vivo to scopolamine without a dehydration step.
Enzyme preparations from cultured roots of H. niger converted Hyos-OH to scopolamine in the presence of co-factors required by 2-oxoglutarate-dependent dioxygenases. Incubations with [6-^<18>O]Hyos-OH and [7 -^2H]Hyos-OH as substrates demonstrated that the epoxidation reaction proceeds with retention of the 6 -hydroxy oxygen and with loss of the 7 -hydrogen. The epoxidase activity found under the optimal reaction conditions studied was considerably lower than the H6H activity in cultured roots, and the two activities could not be separated during partial purification. The function of this epoxidase in scopolamine biosynthesis is discussed in relation to H6H.
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Research Products
(6 results)
