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酶架构:优化过渡状态稳定从一个阴离子-二离子对
Archie C Reyes1, Astrid P Koudelka1, Tina L Amyes1
1Department of Chemistry, University at Buffalo, SUNY, Buffalo, New York 14260-3000, United States.
Journal of the American Chemical Society
|April 18, 2015
概括
糖3-酸脱酶 (GPDH) 使用基质结合能量来稳定过渡状态. 突变揭示了GPDH如何通过静电相互作用积极稳定过渡状态,从而提高催化效率.
科学领域:
- 酶动力学和机制的机制
- 蛋白质工程是一种蛋白质工程.
- 生物化学 生物化学
背景情况:
- 糖3-酸脱酶 (GPDH) 对于细胞能量代谢至关重要.
- GPDH的活性部位涉及酶及其基质二氧酸 (DHAP) 之间的静电相互作用.
- 了解这些相互作用是阐明酶催化机制的关键.
研究的目的:
- 调查R269残留物在GPDH的催化机制中的作用.
- 量化静电相互作用对过渡状态稳定性的贡献.
- 探索如何利用基质结合能量进行催化.
主要方法:
- 用局部导向的突变发生法来创建GPDH的R269A突变.
- 对野生类型和突变酶进行了酶动力学 (K(m) 和k(cat) 测量).
- 评估了 guanidinium 离子对过渡状态稳定性的影响.
主要成果:
- R269A突变显著增加了K ((m) (110倍) 和减少了k ((cat) (41,000倍),使过渡状态不稳定9.1kcal/mol.
- 瓜尼尼离子使R269A突变的过渡状态稳定了6.7kcal/mol.
- 基质碎片的共价附着进一步稳定了野生类型酶的2.4kcal/mol的过渡状态.
结论:
- GPDH利用大约11kcal/mol的DHAP的结合能量,将基质困在一个非极性活性位点中.
- 这种策略允许强大的静电相互作用,通过过渡状态稳定产生9kcal/mol的回报.
- 涉及酶-二离子对的催化动机在实现强大的过渡状态稳定方面广泛适用.
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