リグナンOMTに関する最新研究動向  [in Japanese] Recent Advances in Lignan OMT Studies  [in Japanese]

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Abstract

<p>リグナンは代表的なフェニルプロパノイド系二次代謝産物である。リグナンの化学構造は多様であり,取分け芳香核のメトキシ基の置換様式の多様性が代謝最終産物の構造多様性賦与に大きく効いている。我々はリグナンのフェノール性ヒドロキシ基の<i>O</i>-メチル化を触媒する,いわゆるリグナン<i>O</i>-メチル基転移酵素(OMT)をコードする 遺伝子(cDNA)を従来6種取得してきた。さらに,近年<i>Podophyllum hexandrum</i>から2種のリグナンOMT遺伝子の取得が報告された。これらのリグナンOMTのアミノ酸配列は多様であり,また反応の基質特異性や位置選択性において多様であることから,リグナンOMTは個々の植物種において収斂進化的に進化してきたことが推定される。このことは,今後,有用生理活性リグナンの合成生物学的生産を含め,より詳細なリグニン生合成研究を進めるにあたり,一つの指針を提供すると考えられる。</p>

<p>Lignans are phenylpropanoid dimers, where the phenylpropane units are linked by the central carbon (C8) of their propyl side chains. Lignans vary substantially in the chemical structure of their basic carbon frameworks, oxidation levels, and aromatic substitution patterns. <i>O</i>-Methylation on the aromatic rings is often crucial in determining the final product distribution. In the secondary or specialized metabolic processes of plants, <i>O</i>-methylation is usually catalyzed by <i>S</i>-adenosyl-L- methionine-dependent <i>O</i>-methyltransferases (OMTs). We have so far isolated six cDNAs encoding lignan OMTs: <i>Carthamus tinctorius</i> matairesinol OMT (CtMROMT), <i>Sesamum indicum</i> OMT1 (SiOMT1), <i>Sesamum radiatum</i> OMT1 (SrOMT1), <i>Anthriscus sylvestris</i> matairesinol OMT (AsMROMT), <i>A. sylvestris</i> thujaplicatin OMT (AsTJOMT), and <i>Forsythia koreana</i> matairesinol OMT (FkMROMT). Phylogenetic tree analysis indicated that CtMROMT and AsMROMT formed a small clade with plant OMTs including caffeic acid <i>O</i>-methyltransferase from <i>Rosa chinensis</i> var. <i>spontanea</i> (RcOMT3) and reticuline 7-<i>O</i>-methyltransferase from <i>Papaver somniferum</i> (PsOMT1). By contrast, in the phylogenetic tree SiOMT1 and SrOMT1 were located closely to the clade containing 5-hydroxyconiferaldehyde OMTs [CAldOMTs, caffeic acid OMTs (CAOMTs)]. AsTJOMT and FkMROMT were located in a small clade which is somewhat close to the clade of SiOMT1, SrOMT1, and CAldOMTs. In addition, two lignan OMT genes, <i>PhOMT1</i> and <i>PhOMT3</i>, were detected in <i>Podophyllum hexandrum</i> that is known to produce an antitumor lignan, podophyllotoxin. PhOMT1 showed slight sequence similarity to AsTJOMT and FkMROMT, while PhOMT3 shared low sequence similarity with the other 7 lignan OMTs. These lignan OMTs show diverse substrate specificities and different <i>meta</i>/<i>para</i> selectivity in phenolic <i>O</i>-methylation. Taken together, the lignin OMTs may have arisen independently in various lignan-producing plants via acquisition of substrate specificity for lineage-specific lignan structures. These findings on lignan OMTs provide useful information for further identification of cDNAs encoding other lignan OMTs, as well as clues to understand diversity and plasticity of plant secondary metabolism beyond lignan biosynthesis.</p>

Journal

  • Mokuzai Gakkaishi

    Mokuzai Gakkaishi 65(1), 1-12, 2019

    The Japan Wood Research Society

Codes

  • NII Article ID (NAID)
    130007583761
  • NII NACSIS-CAT ID (NCID)
    AN00240329
  • Text Lang
    JPN
  • ISSN
    0021-4795
  • NDL Article ID
    029480742
  • NDL Call No.
    Z17-484
  • Data Source
    NDL  J-STAGE 
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