α-ケトグルタレット依存型単核非ヘム鉄酵素によるエンドペロキシド形成
Wupeng Yan1, Heng Song2, Fuhang Song3
1Department of Molecular Biosciences, University of Texas at Austin, Austin, Texas 78712, USA.
Nature
|November 3, 2015
まとめ
研究者らは,非ヘム鉄酵素であるAspergillus fumigatus fumitremorgin Bエンドペロキシダース (FtmOx1) によってエンドペロキシド形成の新たなメカニズムを発見した. 主要なチロシン残基は活性部位をシールドし,ヒドロキシル化ではなくエンドペロキシド合成に触媒を向けます.
科学分野:
- 生物化学
- 酵素学
- 構造生物学
背景:
- ペロキシを含む二次代謝物は健康に有益ですが,その生物合成メカニズムは十分に理解されていません.
- プロスタグランジンH合成酵素は,ヘム共因子を利用した,唯一よく特徴づけられたエンドペロキシド生物合成酵素である.
- アスペルギルス・フミガトゥス (Aspergillus fumigatus) のフミトレモルギンBエンドペロキシダース (FtmOx1) は,エンドペロキシド形成を触媒とする,α-ケトグルタレット依存の単核非ヘム鉄酵素である.
研究 の 目的:
- FtmOx1によるエンドペロキシド形成のメカニズムを明らかにする.
- FtmOx1触媒における特定のチロシン残留物 (Y224) の役割を調査する.
- 酵素反応に関与する過渡的な基質種を特徴づける.
主な方法:
- FtmOx1と,α-ケトグルタレートとフミトレモルギンBとの二元複合体のX線結晶学
- Y224残留物のサイト指向型変異
- ストップフロー光学吸収スペクトロスコーピー
- フリーズ・キッチン電子パラマグネティック共振 (EPR) スペクトロスコーピー.
主要な成果:
- 結晶構造は,Y224が酸素活性化部位を遮断する鉄の中心へのα-ケトグルタレットの結合を明らかにした.
- Y224をアラニンまたはフェニララニンに変異させることで,エンドペロキシド形成から水酸化へと触媒が移行した.
- 光譜分析は,FtmOx1触媒の過程で過渡的な根性種の証拠を提供した.
結論:
- FtmOx1は,既知のヘムを含む酵素とは異なる,エンドペロキシド形成のユニークなメカニズムを使用しています.
- Y224残基は,基質の選択性および反応経路の指示において重要な役割を果たします.
- この研究は,エンドペロキシドの生物合成のための中間基を含む新しい酵素経路を明らかにした.
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