在丁氧化降解酶中,酶活性对蛋白质构成的阻断
Hiroshi Ishikita1, Bryan T Eger, Ken Okamoto
1Career-Path Promotion Unit for Young Life Scientists, Kyoto University, 202 Building E, Graduate School of Medicine, Kyoto 606-8501, Japan. hiro@cp.kyoto-u.ac.jp
Journal of the American Chemical Society
|December 8, 2011
概括
桑丁氧化降解酶 (XDH/XO) 酶在电子转移方面有所不同,尽管它们的结构相同. 在flavin位点附近的循环形态变化解释了XDH和XO之间的氧化还原电位差异.
科学领域:
- 生物化学 生物化学
- 酶学 是一种酶学.
- 结构生物学 结构生物学
背景情况:
- 哺乳动物的丁氧化还原酶以丁脱酶 (XDH) 和丁氧化酶 (XO) 的形式存在.
- 这两种酶都有共同的氧化还原辅助因子,形成一个电子转移 (ET) 路径,以弗拉辅助因子结束.
- 尽管主要结构相同,但XDH和XO对于flavin半氨酸/氨酸对 (E(sq/hq)) 的显著~170mV的氧化还原电位差异.
研究的目的:
- 阐明XDH和XO的不同电子转移活动的结构和能量基础.
- 了解该酶如何促进能量上升的电子从FeS-II转移到XDH中没有NAD的flavin.
主要方法:
- 基于XDH,XO和NAD+-/NADH复合XDH的新晶体结构的E (sq/hq) 值的计算,分辨率高达1.65 Å.
- 分析形状变化及其对弗拉辅因子氧化还原潜力的影响.
主要成果:
- XDH和XO之间的E{\sq/hq}差异的主要来源是flavin结合点附近的循环 (残留物423-433),影响半农状态稳定性的形态变化.
- 与XDDH结合的NAD (((+) 并没有诱导显著的大型构造变化.
- 改变E{\sq/hq}对NAD{\+}结合的关键因素包括NAD{\+}环的正电荷,Asp429脱质和flavin表面的NAD{\+}封闭.
结论:
- 在flavin位点附近的一种微妙的环形状变化是XDH和XO之间的功能性氧化还原电位差异的主要驱动因素.
- 结合NAD(+) 调节了XDH中的flavin氧化还原潜力,而不是通过主要的结构重组,而是通过静电和硬体相互作用.
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