窒素酵素触媒と関連したFeタンパク質サイクルには,個々の電子移転イベントごとに2つのATPの水解が必要です

Zhi-Yong Yang¹, Artavazd Badalyan¹, Brian M Hoffman²

¹Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, United States.

Journal of the American Chemical Society

|March 1, 2023

まとめ

窒素酵素の機能はATPの水解に依存している. この研究では,酸化還元状態に関係なく,Feタンパク質成分は窒素固定時にMoFeタンパク質成分に転送される1つの電子ごとに2つのATPを使用していることが示されています.

科学分野:

生物化学
酵素学
バイオエネルギー

背景:

窒素酵素は窒素 (N2) 還元を触媒化し,窒素循環における重要なステップである.
酵素のメカニズムは,Feタンパク質からMoFeタンパク質への電子移転と,ATPの水解を伴う.
Feタンパク質には酸化状態と還元状態の間で循環する [4Fe-4S] クラスタが含まれています.

研究の目的:

Feタンパク質の標準 [4Fe-4S]1+状態と,新たに発見された超減少 [4Fe-4S]0状態における電子移転あたりのATP消費を調査する.
超低減状態が,ナイトロゲンゼの確立されたエネルギー利用モデルを変更するかどうかを判断する.

主な方法:

定常状態の酵素動態測定
Feタンパク質の [4Fe-4S] クラスター酸化還元状態の光譜分析.
ATPの水解と電子移転速度の定量化

主要な成果:

Feタンパク質の [4Fe-4S]1+ 状態と [4Fe-4S]0 状態は,単一の電子移転ごとに2つのATP分子が水解されるという一貫した要求を示している.
電子移転ごとに消費されるATPの数は,Feタンパク質クラスタの初期還酸化状態に関係なく一定である.
Feタンパク質は一度に MoFeタンパク質に 1個の電子しか転送しない.

結論:

窒素酵素のエネルギー結合機構は堅固であり,Feタンパク質の [4Fe-4S] クラスタの酸化還元状態には変化しない.
電子移転ごとに2つのATPが水解されるという確立されたモデルは,Feタンパク質の標準状態と超低減状態の両方に当てはまります.
この発見は,窒素酵素のバイオエネルギーと触媒のサイクルについての理解を強化します.

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