Escherichia coliのピルバート脱水素酶複合体における安定状態前の速度定数の決定は,ループの動きが速度制限ステップを制御することを明らかにします
Anand Balakrishnan1, Natalia S Nemeria, Sumit Chakraborty
1Department of Chemistry, Rutgers the State University, Newark, New Jersey 07102, United States.
Journal of the American Chemical Society
|October 24, 2012
まとめ
ピルバ酸脱水素酶複合体 (PDHc) のE1p成分内のダイナミック領域は,触媒作用において極めて重要です. アクティブサイトループの破壊は,中間形成を大幅に遅らせ,これらのダイナミクスがコヴァレンント触媒を制御することを示しています.
科学分野:
- 酵素学と酵素運動学
- 酵素複合体の構造生物学
- メタボリック・バイオケミストリー
背景:
- ピルバ酸脱水素酵素多酵素複合体 (PDHc) は,炭素代謝の中心にある.
- E1pコンポーネントのダイナミック領域は,PDHcの触媒サイクルを調節すると仮定されています.
- 中間物質の形成を理解することは,PDHc機能の解明の鍵です.
研究 の 目的:
- PDHcおよびその変種における共性中間物質の運動的特徴を特定する.
- PDHc触媒におけるE1pコンポーネントのダイナミック領域の役割を調査する.
- PDHcアセンブリがE1pループのダイナミクスと触媒に影響を与えるかどうかを判断する.
主な方法:
- E1p.上にあるチアミン二酸化塩酸 (ThDP) に結合した中間物質の運動特性.
- PDHcおよび変種内のE2p上のリポアミド結合中間物質の分析.
- E1pコンポーネントのアクティブサイトループのサイト指向型変異.
主要な成果:
- C2α-ラクチルチアミンジホスファート (LThDP) の中間物質の形成は,速度制限として特定されました.
- アクティブサイトループの変異により,LThDP形成率は最大900倍まで低下しました.
- PDHcにE401Kの変種を組み立てると,部分的にLThDP形成速度が回復しました.
結論:
- E1pループのダイナミクスは,ThDPを含むコバルント触媒の制御に不可欠です.
- PDHcアセンブリはこれらのダイナミクスを調節し,おそらく特定のループコンファメーションを選択します.
- このインターフェイスダイナミック領域制御のメカニズムは,2-オキシ酸脱水原酶複合体全体で保存され得る.
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