ディヒドロフォラート還元酵素における結合基質pKaに対する進化的影響
Anil R Mhashal1, Yaron Pshetitsky1, Christopher M Cheatum2
1Department of Chemistry , Bar-Ilan University , Ramat-Gan 5290002 , Israel.
Journal of the American Chemical Society
|November 7, 2018
まとめ
ディヒドロフォラート還元酶 (DHFR) という酵素は 基板により効果的に結合するよう進化した. この研究では 酵素塩基度の増加と活性部位の水分減少が相関しており 進化的適応を示唆しています
科学分野:
- 生物化学
- 酵素学
- 分子 進化
背景:
- ディヒドロフォラート還元酵素 (DHFR) は葉酸代謝に不可欠です.
- DHFRイソフォームの進化を理解すると,酵素適応の洞察が得られます.
- 基質pKa調節は酵素の触媒効率の鍵となる.
研究 の 目的:
- 基質pKaに対するDHFR活性部位構造の影響を調査する.
- DHFRイソフォームの進化傾向を探求する.
- 活性部位の水分と基質の相関性を調べる
主な方法:
- 量子力学/分子力学 (QM/MM) の自由エネルギー乱射法を使用した.
- 7,8-ジヒドロフォレートのN5位置のpKaを計算した.
- 様々なDHFRイソフォームにおける構造的差異と水分子のダイナミクスを分析した.
主要な成果:
- 原始から進化したDHFRイソフォームへのN5塩基性の漸進的な増加が観察されました.
- 活性部位の水分補給が低下し,N5 pKaが増加したとの相関が認められた.
- 活性部位の水性と柔軟性を調節するM20ループの役割を特定した.
結論:
- 活性部位の水分化レベルは,結合した7,8-二水素葉酸のpKaに直接影響する.
- DHFRの進化過程は,活性部位の水分排除を伴い,基板への結合を強める.
- M20ループは活性部位の水分化と酵素の進化を調節する重要な構造要素です.
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