银氧化酶作为铜超氧化物中心反应性的模型
Kristi J Humphreys1, Liviu M Mirica, Yi Wang
1Department of Chemistry, University of California, Berkeley, California 94720, USA.
Journal of the American Chemical Society
|March 18, 2009
概括
使用同位素效应研究了银河糖氧化酶酶活性. 在氧化半反应中,从辅因子到铜-超氧介质的原子转移是决定速度的.
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:
- 银酸氧化酶是一种参与碳水化合物代谢的单核铜酶.
- 了解其催化机制,特别是氧化半反应,对于酶功能研究至关重要.
- 之前的研究已经提出了各种机制,但速度决定的步骤需要进一步阐明.
研究的目的:
- 为了研究银河糖氧化酶氧化半反应的速度决定性步骤.
- 使用基质和溶剂和O-18同位素效应探测该机制.
- 描述反应性铜-超氧中间体,并将其与相关酶进行比较.
主要方法:
- 使用O(2) 消耗的平稳状态动力学测定.
- 使用1-O-甲基-α-D-galactopyranoside作为糖基质.
- 测量基质和溶剂同位素效应和O-18动态同位素对k(cat) /K(m) 的影响.
主要成果:
- 一个乒乓球机制被证实为反应.
- 一个显著的基质同位素效应 (32) 被观察到 k 猫/K m S .
- 较小的同位素效应 (1.6-1.9) 和O-18同位素效应 (1.0185) 在k(cat) /K(m) ((O(2)) 上表明从辅因子到Cu(II) -超中间体的原子转移作为速率决定.
结论:
- 从被减少的辅因子转移到Cu(II) -超氧中间体的原子转移是氧化半反应中速度决定的步骤.
- O-18同位素效应提供了该酶家族中反应性超氧物种的证据.
- 在银河糖氧化酶的还原和氧化半反应期间,转移存在根本的差异.
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