ケトステロイドイソメラーゼによる酵素強化結合運動/量子力学水素トンネリングの実験的証拠
Thomas C Wilde1, Grzegorz Blotny, Ralph M Pollack
1Department of Chemistry and Biochemistry, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, Maryland 21250, USA.
Journal of the American Chemical Society
|April 23, 2008
まとめ
この研究では,酵素および非酵素反応における量子力学的水素トンネリング (HT) を調査した. 結果は,3-オクソ-デルタ(5) -ステロイドイソメラーゼ (KSI) がHTを強化し,その触媒速度加速に貢献することを示しています.
科学分野:
- バイオケミストリー バイオケミストリー
- 酵素の動力学について
- 量子力学は,量子力学という
背景:
- 量子力学的水素トンネリング (HT) は,酵素系と非酵素系の両方で観察されています.
- 酵素がHTを非酵素反応と比較して強化するかどうかに関するデータは限られている.
研究 の 目的:
- 3-oxo-Delta(5) -ステロイドイソメラーゼ (KSI) が,アセテット触媒反応に比べて,水素トンネリング (HT) を強化するかどうかを決定する.
- KSI.の速度加速に対する結合運動/HTの寄与を調査する.
主な方法:
- ステロイドのC-6で測定されたアルファ二次デウテリウム運動同位体効果 (KIE) は,KSIおよびアセテット触媒による同位体化の両方で測定された.
- デュテリウム移転条件下で二次的なKIEを測定することによって,結合運動/HTの寄与を評価した.
- 野生型 (WT) KSIと活性サイト変異体 (Y14F,D99A) のKIEデータを分析した.
主要な成果:
- WT KSIとアセテットの通常の二次KIEは,両方のシステムで結合運動/HTを示唆しています.
- デュテリウム移転中のWT KSIのための二次的なKIEの減少は,酵素反応におけるHTを示しています.
- アセテート反応における二次KIEの変化がないことは,HTがないことを示しており,KSIがCM/HTを強化することを示唆しています.
- KSIの活性部位変異体は,WTに類似したKIEsを示し,水素結合残留物はCM/HTの寄与にとって重要ではないことを示唆しています.
結論:
- KSIは,溶液反応と比較して,その触媒速度加速に結合運動/水素トンネリング (CM/HT) の貢献を強化します.
- 酵素の活性部位は,強化された量子力学的トンネリングを促進します.
- 主要な活性部位残基の変異は,CM/HTを強化する酵素の能力を有意に低下させない.
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