アルギニンキナーゼのミカエリス複合体は,触媒速度に一致する周波数で移行状態をサンプリングします
Yu Peng, Alexandar L Hansen, Lei Bruschweiler-Li
1Department of Biochemistry and Molecular Biology, Oregon Health and Science University , Portland, Oregon 97239, United States.
Journal of the American Chemical Society
|March 14, 2017
まとめ
アルギニンキナーゼ (AK) ダイナミクスは,反応速度を決定する移行状態へのミカエリス複合アナログチャネルを明らかにする. 移行状態のアナログは,ミカエリス状態とアポ状態を相互にサンプルし,酵素触媒機構を明確にします.
科学分野:
- 生物化学
- 酵素運動
- 構造的動態
背景:
- アルギニンキナーゼ (AK) は,フォスファゲンキナーゼの一種である.
- AKは様々な状態における酵素触媒のモデルとして機能する.
- キー状態には,アポ,ミカエリス複合アナログ (MCA),製品複合アナログ (PCA),および移行状態アナログ (TSA) が含まれる.
研究 の 目的:
- AKにおける酵素触媒の構造的および動的決定因子を調査する.
- 酵素のサイクル状態における AKの構成動態を解明する.
- これらのダイナミクスがアルギニンリン酸化の反応速度にどのように影響するかを理解する.
主な方法:
- NMR リラクゼーション分散測定を用いた.
- Ile,Leu,Valのメチル群の残留をモニターした.
- 測定は2つの静的な磁場で行われました.
主要な成果:
- すべての研究された状態は,重要なμs-ms時間スケールダイナミクスを表しています.
- MCAのみが,過渡状態のような興奮状態を圧倒的に検取します.
- MCAのリラクゼーション分散と均衡化学シフトの違いは強い相関関係にある.
- MCAの平均寿命は36 msで,TSAのような形態と8.5 kJ/molの自由エネルギー差がある.
- TSAは相互にMCAまたはapo状態のサンプルを取ります.
結論:
- MCAのコンフォメーションエネルギーランドスケープは,移行状態への移行を指示し,速度を制限するステップを指示します.
- 移行状態の自由エネルギーは,ミカエリスやアポ複合体の形状よりもわずかに低い.
- これらの発見は,酵素触媒の動的制御に関する洞察を提供します.
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