ラジカルSAM酵素のピルバート形式酵素活性化
Krista A Shisler1, Rachel U Hutcheson1, Masaki Horitani2
1Department of Chemistry and Biochemistry, Montana State University , Bozeman, Montana 59717, United States.
Journal of the American Chemical Society
|August 4, 2017
まとめ
ピル酸塩形式酵素活性化酵素 (PFL-AE) は,活性化のために単価イオンを必要とします. このカチオンは,S-アデノシル-l-メチオニン (SAM) と鉄硫黄群との相互作用によって酵素機能を最適化します.
科学分野:
- 生物化学
- 酵素学
- 構造生物学
背景:
- ピルバ酸フォーマットライアス活性化酵素 (PFL-AE) は,ピルバ酸フォーマットライアスのグリシル基を生成するために不可欠です.
- ラジカルS-アデノシル-l-メチオニン (SAM) 酵素は,ビタミンB12依存酵素とメカニズム的な類似性を共有しています.
研究 の 目的:
- PFL-AEの単価イオン結合部位を特徴づけるために.
- 酵素の活性とメカニズムにおけるこのカチオンの役割を明らかにする.
- カチオンとSAMコスブストラットと鉄硫黄の相互作用を調査する.
主な方法:
- 構造の決定のためのX線結晶学.
- 溶液状態分析のためのパルス電子核二重共振 (ENDOR) スペクトロスコーピー.
- 電子パラマグネティック共振 (EPR) と円形二極化 (CD) のスペクトロスコーピーを用いて電子特性を評価する.
- 酵素の活性を評価する生化学的測定法
主要な成果:
- PFL-AEは,結晶構造ではNa+,溶液では23Naと識別される,触媒的に必須の単価イオン (M+) を活性部位で結合する.
- カチオンは,SAMカルボキシラート酸素と相互作用し,SAMケラート鉄硫黄の電子特性を影響する.
- 酵素の活性度はカチオン型に大きく依存し,K+とNH4+の最適活性が見られる.
結論:
- PFL-AEはタイプIのM+活性化酵素で,カチオンはSAMとの相互作用によって反応性を調節する.
- カチオンの存在とアイデンティティは,PFL-AEの触媒機能にとって極めて重要です.
- このカチオン依存メカニズムは,SAM酵素のレギュレーションに関する新しい洞察を提供します.
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