酸化窒素合成酵素の結合基体はプロトン化か中性か,基質の水酸化を行う活性酸化剤はどれか
Sam P de Visser1, Lee Siew Tan
1Manchester Interdisciplinary Biocenter and the School of Chemical Engineering and Analytical Science, The University of Manchester, 131 Princess Street, Manchester, M1 7DN, United Kingdom. sam.devisser@manchester.ac.uk
Journal of the American Chemical Society
|September 9, 2008
まとめ
密度関数理論の研究は,酸化窒素合成酵素 (NOS) が新しい経路でL-アルギニンを水酸化することを明らかにしています. 化合物IIは重要な酸化物質であり,シトクロームP450のメカニズムと異なる.
科学分野:
- バイオケミストリーと酵素学
- 計算化学はコンピュータ化学である.
- 機械的酵素学 機械的酵素学
背景:
- 酸化窒素合成酵素 (NOS) は,L-アルギニンのN (オメガ) -ヒドロキソアルギニンへの水酸化を触媒化する.
- NOSの触媒機構は,シトクロームP450酵素の触媒機構に似ていると考えられている.
- NOSの触媒サイクルにおける正確なステップを理解することは,酵素機能の解明に極めて重要です.
研究 の 目的:
- 密度関数理論 (DFT) を用いて,酸化窒素合成酵素 (NOS) 触媒サイクルにおける重要なステップを調査する.
- NOSによるL-アルギニンの水酸化のメカニズムを解明する.
- NOSメカニズムとサイトクロームP450酵素のメカニズムを比較する.
主な方法:
- 密度関数理論 (DFT) の計算は,NOS.の酵素活性部位モデルで実行されました.
- 反応経路,移行状態,および中間エネルギーの分析.
- 陽子伝送機構と電子構造が調査されました.
主要な成果:
- L-アルギニンの水酸化のための低エネルギー経路が特定され,シトクロームP450.0と異なる.
- 基質L-アルギニンは,陽子ドナーと水酸化物種の両方で作用する.
- 化合物IIは,活性鉄種の縮小形であり,P450とは異なり,NOSの主要な酸化物質として特定されました.
結論:
- NOS酵素は,アルギニンヒドロキシル化のためのユニークな触媒機構を採用し,化合物IIが活性酸化物質である.
- 提案されたメカニズムは,アルギニンから化合物Iへ最初の電子移転を行い,化合物IIを形成し,次に水素抽出と急性再結合を行います.
- タンパク質の環境の影響は,反応機構のエネルギーに最小限の影響を及ぼします.
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