人間の炭酸アンヒドラゼIIにおける陽子輸送機構の解明

C Mark Maupin¹, Robert McKenna, David N Silverman

¹Center for Biophysical Modeling and Simulation and Department of Chemistry, University of Utah, Salt Lake City, Utah 84112, USA.

Journal of the American Chemical Society

|May 15, 2009

まとめ

ヒト炭酸アンヒドラゼIIは,素子輸送のために水クラスタを使用しており,これは素早く酵素活性化するために不可欠です. His64の向きと水クラスタの安定性は,この速度制限ステップに大きく影響する.

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
コンピューティング・ケミストリー

背景:

人間の炭酸アンヒドラゼII (HCA II) は,非常に効率的な酵素である.
その触媒機構には,速度を制限する陽子輸送 (PT) ステップが含まれています.
このPTステップを理解することは,酵素機能の鍵です.

研究の目的:

HCA II.における陽子輸送イベントの原子学的詳細を調査する.
PTにおけるアクティブサイト・ウォーター・クラスターの役割とHis64の指向を評価する.
速度制限ステップを制御する要因を解明する.

主な方法:

マルチステート・エンパイリカル・ヴァレンンス・ボンド (MS-EVB) 計算方法.
陽子輸送の原子レベルシミュレーション.
異なる His64 オリエンテーションの自由エネルギーバリアの分析.

主要な成果:

HCA IIは,陽子輸送のために一時的なアクティブサイト水クラスタを使用します.
陽子の移転は,亜鉛結合水/水酸化物とHis64.4の間で行われます.
PTは,水のクラスター形成とHis64の方向性に依存しています.
彼の64の方向性は,PT自由エネルギー障壁に直接影響を及ぼします.
His64の相互作用がない状態で3つの異なる陽子入出路を特定した.

結論:

アクティブサイトの水群とHis64の方向性は,HCA IIの陽子輸送効率に極めて重要です.
速度を制限するステップは,His64とHis64のプロトン移転と/de/protonationの間でシフトすることができます.
発見は,酵素-水インターフェースとHCA II変異体研究に関する洞察を提供します.

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