在光合作用氧进化复合体中,质子合电子转移和氧化还原活性氨酸Z
James M Keough1, David L Jenson, Ashley N Zuniga
1School of Chemistry and Biochemistry and the Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
Journal of the American Chemical Society
|July 1, 2011
概括
光系II (PSII) 中的质子合电子转移 (PCET) 区分了YZ和YD的氧化还原活性氨酸. YZ PCET是pH独立的,并显示了溶剂同位素效应,暗示了合的质子电子转移机制.
科学领域:
- 生物化学 生物化学
- 光合作用研究研究 光合作用研究
- 酶的机制 酶的机制
背景情况:
- 质子合电子转移 (PCET) 在酶反应中至关重要,通常涉及氧化还原活性氨酸.
- 光系统II (PSII) 使用两个有氧还原活性氨酸,YD和YZ,具有不同的催化作用.
- YZ对于氧的进化至关重要,并且由催化场迅速减少.
研究的目的:
- 研究YZ PCET在氧化演化PSII中的机制.
- 描述YZ(•) 衰变动力学及其对pH值和溶剂同位素效应的依赖.
- 在PSII中区分YZ和YD的PCET机制.
主要方法:
- 利用低温来隔离YZ(•) 反应,同时保留-集群.
- 使用高的微波功率来和YD的EPR信号.
- 使用EPR光谱测量了YZ(•) 衰变动力学,并分析了pH和溶剂同位素依赖性.
主要成果:
- YZ(•) 衰变速率表现出显著的溶剂同位素效应.
- 在pH 5.0和7.5.5之间,YZ(•) 重组的速率和溶剂同位素效应与pH无关.
- 这些发现与在低pH下观察到的YD () 衰变动力学形成对比.
结论:
- 具有溶剂同位素效应的pH独立YZ(•) 衰变支持限制速率的合质子电子转移 (CPET) 机制.
- 围绕YZ的一个广泛的键网络可能会调解这个CPET过程.
- 在PCET反应中,可以明显区分YZ和YD在PSII中的功能作用.
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