五价器官瓦纳基作为酸转移反应的过渡状态类似物
June M Messmore1, Ronald T Raines
1Contribution from the Department of Biochemistry and Department of Chemistry , University of Wisconsin-Madison, Madison, WI 53706.
Journal of the American Chemical Society
|March 23, 2011
概括
五价性有机瓦纳酸盐,如尿素2 2
科学领域:
- 生物化学 生物化学
- 酶动力学 酶动力学
- 化学生物学是化学生物学.
背景情况:
- 五价性有机酸盐被提议作为酸转移反应的过渡状态类似物.
- 尿素2',3'-循环瓦纳酸盐 (U>v) 假设模仿核糖酶A (RNase A) 过渡状态.
- 在RNase A中的Lys41对于通过键稳定过渡状态至关重要.
研究的目的:
- 实验测试假设U>v是RNase A的过渡状态模拟.
- 为了研究U>v与RNase A催化过渡状态相似的程度.
- 在严格的过渡状态分析中评估五价位器官-瓦纳基的实用性.
主要方法:
- 局部导向的突变发生和半合成,在Lys41.1.中产生RNase A变体.
- 酶动力学试验测量催化速率 (kcat/Km) 和抑制常数 (Ki).
- 使用logKi vs log(Km/kcat) 图表对过渡状态模拟属性的分析.
主要成果:
- 在Lys41中,RNase A变体在催化活性 (10^5倍) 中表现出很大的差异,但在U>v抑制 (<40倍) 中表现出较小的差异.
- 在LogKi与log ((Km/kcat) 图片中,斜率在0.25和0.36之间,偏离了理想的单位值.
- 对于U>v的ki值显示与基质/产品结合常数的相关性较弱.
结论:
- 尿素2',3'-循环瓦纳酸盐 (U>v) 是对核糖核酶A (RNase A) 的边缘过渡状态类似物.
- 五价性器官-瓦纳酸可能并不总是用于转移反应的精确过渡状态类似物.
- 该研究强调了在酶催化过程中使用瓦纳达酸盐进行详细的过渡状态分析的局限性.
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