ベータ-ラクタムと類似したベータ-スルタムとセリンベータ-ラクタマゼの反応の異なる移行状態構造
Wing Y Tsang1, Naveed Ahmed, Paul S Hinchliffe
1Department of Chemical and Biological Sciences, The University of Huddersfield, Queensgate, Huddersfield, HD1 3DH, UK.
Journal of the American Chemical Society
|December 8, 2005
まとめ
N-アシルβ-スルタムは,スルフォニレーションによってCクラスβ-ラクタマースを無活性化し,メカニズム的にはβ-ラクタムと異なる. これらの新種の不活性化剤は,酵素反応における異なった移行状態を明らかにし,β-ラクタマース阻害に関する洞察を提供します.
科学分野:
- バイオケミストリー バイオケミストリー
- 酵素学 酵素学とは
- 薬用化学 薬用化学について
背景:
- ベータ・ラクトームは重要な抗生物質ですが,ベータ・ラクトーマゼによって媒介される耐性には新しい阻害剤が必要になります.
- ベータ-ラクタムのサルフォニル類のベータ-スルタムは,酵素不活性化剤の潜在的なクラスを表しています.
- Enterobacter cloacae P99からのCクラスβ-ラクタメーゼは,抗生物質耐性研究にとって重要なターゲットです.
研究 の 目的:
- N-アシルβ-スルタムスがC級β-ラクタマゼを無効化するメカニズムを調査する.
- 酵素によるβ-スルタム硫化とβ-ラクタム水解の反応動態と移行状態を比較する.
- 酵素阻害における脱出グループと移行状態構造の役割を明らかにする.
主な方法:
- 精製されたC級β-ラクタマースによるN-アシルβ-スルタムおよびN-アシルβ-ラクタムを用いた酵素運動の研究.
- 不活性化 (k ((i)) と水解 (kcat/K ((m)) の二次速度定数の決定.
- 電気スプレー・イオン化質量スペクトロメトリ (ESI-MS) を用いて,反応中介物質と反応産物の特徴を決定する.
- pH依存とブロンステッドβ (lg) 値の分析により,移行状態の特性を探求する.
主要な成果:
- N-アシルβ-スルタムは,新種の無活性化剤として作用し,活性部位セリンで硫酸エステルを形成する.
- この反応はC-O結合分裂とデヒドロアラニン形成を経由して進行し,β-ラクタムの水解とは異なる.
- ベータ-スルタムによる酵素触媒反応は,ヒドロキシド触媒による水解と比較して遅い移行状態を示し,S-N結合の有意な分裂を示している.
- ベータ-スルタム硫化 (-1.46) のブロンステッドベータ (lg) 値は,ベータ-ラクタム水解 (-0.06) と著しく異なっており,メカニズム的な相違を強調しています.
結論:
- N-アシルβ-スルタムは,硫化メカニズムを通じたクラスCβ-ラクタマースの有効な阻害剤である.
- この酵素は,β-ラクタムの水解と比較して,β-スルタムの無活性化に際して,異なる移行状態を利用します.
- これらのメカニズム的な違いを理解することで,新しいβ-ラクタマース阻害剤の設計を導くことができます.
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