The first committed step reaction of caffeine biosynthesis: 7‐methylxanthosine synthase is closely homologous to caffeine synthases in coffee (Coffea arabica L.)1

FEBS Letters

Kato, Misako⁴  Fujimura, Tatsuhito³  Irino, Fumi⁴  Mizuno, Kouichi²  Ashihara, Hiroshi¹  Yoneyama, Naho⁴ 

[1] Department of Biology, Faculty of Science, Ochanomizu University, Otsuka, Bunkyo-ku, Tokyo 112-8610, Japan;Faculty of Bioresource Sciences, Akita Prefectural University, Akita City, Akita 010-0195, Japan;Institute of Agricultural and Forest Engineering, University of Tsukuba, Tsukuba Science City, Ibaraki 305-8572, Japan;Graduate School of Humanities and Sciences, Ochanomizu University, Otsuka, Bunkyo-ku, Tokyo 112-8610, Japan

关键词: Coffee;    Caffeine;    N-methyltransferase;    7-Methylxanthosine;    S-adenosyl-L-methionine;    Xanthosine;    CS;    caffeine synthase;    CtCS;    coffee tentative caffeine synthase;    CTS;    coffee theobromine synthase;    mXRS;    7-methylxanthosine synthase;    RACE;    rapid amplification of cDNA ends;    SAM;    S-adenosyl-L-methionine;    TCS;    tea caffeine synthase;    XMP;    xanthosine 5′-monophosphate;   

DOI  :  10.1016/S0014-5793(03)00670-7

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

In coffee and tea plants, caffeine is synthesized from xanthosine via a pathway that has three methylation steps. We identified and characterized the gene encoding the enzyme for the first methylation step of caffeine biosynthesis. The full-length cDNA of coffee tentative caffeine synthase 1, CtCS1, previously isolated by the rapid amplification of cDNA ends was translated with an Escherichia coli expression system and the resultant recombinant protein was purified using Ni-NTA column. The protein renamed CmXRS1 has 7-methylxanthine synthase (xanthosine:S-adenosyl-L-methionine methyltransferase) activity. CmXRS1 was specific for xanthosine and xanthosine 5′-monophosphate (XMP) could not be used as a substrate. The K _m value for xanthosine was 73.7 μM. CmXRS1 is homologous to coffee genes encoding enzymes for the second and third methylation steps of caffeine biosynthesis.

【 授权许可】

Unknown