18O 動態同位体効果は,リン酸脱水素酵素触媒化リン酸移転の関連移行状態を明らかにする
Graeme W Howe1,2, Wilfred A van der Donk1,2,3
1Department of Chemistry , University of Illinois at Urbana-Champaign , 600 South Mathews Avenue , Urbana , Illinois 61801 , United States.
Journal of the American Chemical Society
|December 12, 2018
まとめ
リン酸脱水酵素 (PTDH) は,他のリン酸加工酵素とは異なり,リン酸移転のための関連メカニズムを使用する. これは,核愛性の重要な参加と,貧しい水素離脱基による緊密な移行状態を伴う.
科学分野:
- 生物化学
- 酵素運動
- バイオ有機化学
背景:
- リン酸脱水酵素 (PTDH) は,ヒドリド離脱基を含むユニークなリン酸転移反応を触媒化する.
- PTDHの触媒メカニズム (関連性対離散性) は,著しい研究努力にもかかわらず,まだ十分に理解されていません.
研究 の 目的:
- 熱安定型PTDH (17X-PTDH) の過渡状態 (TS) を特徴づけることで,その触媒メカニズムを解明する.
- PTDHの触媒が関連性または分離性経路を介して進行するかどうかを判断する.
主な方法:
- 主要な2Hと二次的な18Oの運動同位体効果 (KIEs) の決定
- 酵素の活性部位内の様々な移行状態構造の計算モデル化.
- 計算された移行状態を検証するための2Hと18OKIEsの予測.
主要な成果:
- 大規模で正常な18OKIEは,結合的触媒メカニズムを強く示す.
- 計算分析は,実質的な核愛参加を持つ緊密な移行状態をサポートします.
- 観察されたメカニズムは,フォスファート単体およびダイステル反応に典型的な解離性移行状態と対照的である.
結論:
- 17X-PTDHは,アソシエーションメカニズムを通じて,リン酸の移転を触媒化する.
- 酵素の移行状態は,制限された脱出グループ移動と重要な核愛性の攻撃によって特徴付けられます.
- このユニークなメカニズムは,強いP-O結合を形成するヒドリドの弱い脱出グループ能力に起因する.
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