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酵素が水素トンネリングを強化するために進化したという仮説の最初の実験テスト
Kenneth M Doll1, Bruce R Bender, Richard G Finke
1Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, USA.
Journal of the American Chemical Society
|September 4, 2003
まとめ
この研究では,酵素が量子トンネリングを強化するかどうかをテストし,コエンザイムB12依存酵素が水素トンネリングを強化しないことを発見しました. 代わりに,酵素は,酵素フリー反応で観察された同じ量子トンネリングを使用します.
科学分野:
- バイオケミストリー バイオケミストリー
- 物理化学 物理化学
- 酵素触媒は,酵素触媒として作用する.
背景:
- 酵素触媒には,量子力学的トンネリングが含まれることがあります.
- 強化された酵素駆動トンネリングの仮説は,実験的なテストを必要とします.
- アデノシルコバラミン (AdoCbl) に依存する酵素は,生物学的反応において極めて重要です.
研究 の 目的:
- 酵素が量子力学的トンネリングを強化するという仮説を実験的に検証する.
- AdoCbl依存反応の水素トンネリングを酵素と共に,またはそれなしに比較する.
- ダイオル脱水酵素モデル反応における量子トンネリングの役割を調査する.
主な方法:
- Ado(*) と8-MeOAdo(*) を用いてエチレングリコールからH/D原子抽出を研究した.
- AdoCblと8-MeOAdoCblの前駆体であるCo-C熱分解によって生成されたラジカル.
- 温度範囲 (80-120°C) で測定されたデュテリウム運動同位体効果 (KIEs).
主要な成果:
- 酵素フリー反応における有意な量子力学的トンネリングが観察された.
- 測定されたKIEsと派生パラメータ ([E(D) - E(H) ],A(H) /A(D)) は,実質的なトンネリングを示した.
- 酵素反応データと酵素無反応データは,実験誤差の範囲内で同一であった.
結論:
- 研究されたAdoCbl依存酵素は,量子力学的トンネリングを強化しません.
- 酵素は,溶液ベースの反応に存在する固有の量子トンネリングを利用します.
- 酵素と無酵素の反応は,H抽象化のための類似の障壁の高さと幅を示します.
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