保存された2つ目の球体残留は,リチウムポリサッカリドモノオキシゲネーゼにおける銅部位の反応性を示している
Kelsi R Hall1, Chris Joseph2, Iván Ayuso-Fernández1
1Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), 1432, Ås, Norway.
Journal of the American Chemical Society
|August 16, 2023
まとめ
銅の中心近くの保存されたグルタミン/グルタミン酸残基は,リチウムポリサッカリド単酸化酵素 (LPMO) の機能を微調整する. 変異は酵素の反応性,安定性,触媒メカニズムに影響を与え,LPMOの活性と合成触媒の設計に関する洞察を提供します.
科学分野:
- 生物化学
- 酵素学
- バイオ有機化学
背景:
- リン酸ポリサカリド単酸化酵素 (LPMOs) は,C-H結合を活性化するメカニズムが十分に理解されていない銅酵素である.
- 保存されたグルタミン/グルタミン酸残基は,銅中心の第2の調整球に位置しています.
研究 の 目的:
- 保存されたグルタミン/グルタミン酸残基がLPMOの機能と銅の反応性における役割を調査する.
- この残留物の変異がLPMOの触媒機構と安定性にどのように影響するかを決定する.
主な方法:
- *Nc*AA9CのGln残基からGlu,Asp,またはAsnへのサイト指向型変異.
- 還元能力と再酸化率の測定を含む酵素活性測定
- 電子パラマグネティック共振 (EPR) とX線吸収光譜 (XAS)
- 密度関数理論 (DFT) の計算
主要な成果:
- 遺伝子変異によりLPMOの機能と銅の反応性が変化し,Glu/Aspの接近により還元ポテンシャルと還元/再酸化率の比率が低下した.
- ミュータントは 酵素の不活性化が増加し 穴を飛び越えるための 保護経路が変化しました
- EPRとXASは,突然変異がCu (II) リガンドフィールドを直接混乱させないことを示した.
- DFTの計算では,Gluのプロトネーションが再酸化率を高め,プロトネーションされたGluの形態のためのCu (III) -水酸化物中間物質を明らかにした.
結論:
- 第2球のグルタミン/グルタミン酸残留はLPMOの触媒機能の決定的要素である.
- この残留物は,銅の反応性,酵素の安定性,および反応中間物質に影響します.
- 発見は,LPMOを理解し,新しい合成触媒を設計するための洞察を提供します.
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