| Project/Area Number |
14540590
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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 |
植物生理
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| Research Institution | Ochanomizu University |
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Principal Investigator |
MIZUNO Misako Ochanomizu University, Graduate School of Humanities and Sciences, Associate professor, 大学院・人間文化研究科, 助教授 (60272738)
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| Project Period (FY) |
2002 – 2003
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| Project Status |
Completed (Fiscal Year 2003)
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| Budget Amount *help |
¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2003: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2002: ¥2,700,000 (Direct Cost: ¥2,700,000)
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| Keywords | caffeine / caffeine synthase / theobromine synthase / tea / coffee / cacao / purine alkaloids / N-methyltransferase / カフェインシンターゼ |
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| Research Abstract |
Caffeine (1,3,7-trimethylxanthine) is a purine alkaloid present in high concentrations in tea and coffee. The available data support the operation of a xanthosine→7-methylxanthosine→7-methylxanthine→theobromine→caffeine pathway as the major route to caffeine. We isolated coffee caffeine synthase and 7-methylxanthosine genes and characterized the recombinant enzyme. Caffeine synthase had both 1N-and 3-N-methyltransferase activity, on the other hand, 7-methylxanthosine synthase catalyzed only from Theobroma cacao which accumulated theobromine rather than caffeine. The accumulation of purine alkaloids is therefore, depend on N-methyltransferase substrate specificity. There were no signal sequences in caffeine synthase family, suggesting that they were localized in cytoplasm.
Caffeine synthase and theobromine synthase derived from the same genera are highly homologous with each other. In order to clarify the region related to the region related to the substrate specificity, we produced the recombinant enzyme introduced to the artificial modification in amino acid sequence with E. coli expression system. The residues from 148 to 287 out of 369 amino acids in tea caffeine synthase (TCS1) determined the substrate specificity, in particular, position 221 arginine was contributed to the specificity.
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