在 silico 中探索核酸酶催化:对酶结合基质和过渡状态的分子动力学研究
Devleena Mazumder1, Thomas C Bruice
1Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California 93106, USA.
分子动力学模拟显示Tyr229,而不是His241,作为 inosine-uridine核酸酸酶的质子源. 他的241Ala突变破坏了这个关键的结网络,减少了酶活性.
科学领域:
- 生物化学 生物化学
- 酶学 是一种酶学.
- 计算生物学 计算生物学
背景情况:
- 核酸化酶酶的inosine-uridine核酸化酶在核酸代谢中发挥着至关重要的作用.
- 了解它的作用机制对于药物开发和生物化学研究至关重要.
- 之前的研究表明His241是关键的催化残留物.
研究的目的:
- 为了阐明 inosine-uridine核酸酸酶的详细机制.
- 为了研究His241在酶的催化活性中的特定作用.
- 探索Tyr229的功能和活性位点结网络.
主要方法:
- 使用了长期分子动力学 (MD) 模拟.
- 使用TIP3P水和随机边界条件进行了模拟.
- 模拟了五种不同的酶基质和酶过渡状态复合体,包括一个His241Ala突变体.
主要成果:
- 分子动力学模拟表明Tyr229,而不是His241,作为离开核基的质子源.
- His241Ala突变通过破坏 Tyr229.9 涉及的活性部位结网络,显著降低了酶活性.
- 对His241的质子化没有改变酶复杂结构,这是一个意想不到的发现.
- 该酶表现出钟形的pH依赖性,与Asp10/Asp15解离和Tyr229质子化状态有关.
- 稳定ribusoxocarbenium离子中间体涉及Asn168和Asp14,其中Asp14在仿真时间96%的时间与ribose2'-OH结合.
- 一种涉及水和酸盐残留物 (Asp10,Asp15) 的质子穿机制可能有助于水对核友的攻击.
结论:
- Tyr229是 inosine-uridine核酸酸酶的催化机制中的主要质子捐赠体.
- 结网的完整性,特别是涉及Tyr229的完整性,对于酶的功能至关重要.
- 对Tyr229和Asn168之间的反相关运动的进一步调查可能会揭示近距离攻击形状的洞察力.
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