Zn对乙辅酶a合成酶的影响:证据表明,在催化过程中,α子单元的构造变化发生了
Xiangshi Tan1, Matthew R Bramlett, Paul A Lindahl
1Department of Chemistry, Texas A & M University, College Station, Texas 77843, USA.
Journal of the American Chemical Society
|May 13, 2004
概括
(Zn) 通过替换性Nip金属部位,使-CoA合成酶 (ACS) 不活化. 这种Zn诱导的无活化发生在催化过程中,这表明ACSα子单元的构造变化对其机制至关重要.
科学领域:
- 生物化学 生物化学
- 酶学 是一种酶学.
- 生物有机化学 生物有机化学
背景情况:
- 乙-CoA合成酶 (ACS) 是一种具有复杂活性位点 (A-集群) 的α2β2四聚合物.
- 该A星团包含一个Fe4S4cubane桥接到{Nip Nid}双核站点在阿尔法子单位.
- 阿尔法子单位存在于开放的 (Nip暴露) 和闭合的 (Nip埋藏) 形状,Nip可以被铜 (Cu) 等其他金属所取代.
研究的目的:
- 为了研究 (Zn) 对乙-CoA合成酶 (ACS) 的结构和功能的影响.
- 确定Zn与ACS活性部位相互作用的机制和条件.
主要方法:
- 酶活性测定测量甲基组接受度从电铁硫蛋白 (CoFeSP).
- 电子偏磁共振 (EPR) 光谱检测NiFeC信号.
- 尼普的Zn替代的动态分析.
主要成果:
- 替换Nip的Zn使得ACS变得不活跃,阻止甲基组的接受和NiFeC EPR信号.
- 结合的ACS不能通过添加Ni来重新激活.
- 在催化过程中,Zn专门取代了Nip,这表明中间催化状态很容易受到影响.
- 的替代被EDTA阻断,表明一个金属依赖的过程.
结论:
- 通过不可逆转地替换可变的Nip部位,Zn使ACS无活化,这可能是由于Zn的低核友性.
- Zn-Nip相互作用是依赖于构造的,当α子单元处于开放状态时会发生.
- 在ACSα子单元中,催化依赖的形状变化起着机械作用,而开放的形状易受Zn攻击.
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