Tyrosyl radicals in enzyme catalysis: Some properties and a focus on photosynthetic water oxidation
Tyrosyl radicals in enzyme catalysis: Some properties and a focus on photosynthetic water oxidation
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DOI：
10.3891/acta.chem.scand.51-0533
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发表时间：
1997-05-01
期刊：
影响因子：
--
通讯作者：
Warncke, K
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文献类型：
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作者：
Babcock, GT;Espe, M;Warncke, K
需要氧化还原活性氨基酸进行催化或发挥功能的酶已经成为一类独特的蛋白质。对于酪氨酸为基础的自由基酶，我们表明，自由基中的自旋密度分布遵循一个奇怪的交替模式，是不变的，在10%的类。自由基酶的一般性质进行了总结，从中我们得出结论，它们在催化中的基本作用是启动底物代谢的氢原子提取。这些想法被扩展到光系统II中的Y-Z和Y-D酪氨酸，并讨论了水氧化的自由基氢原子提取模型。在各种条件下，反应中心叶绿素P680（+）氧化Y-Z和Y-D的速率差异被认为是合理的，其基础是由局部蛋白质结构和结合底物水的（Mn）（4）簇的存在或不存在诱导的重组能的变化。
Enzymes that require a redox-active amino acid for catalysis or function have emerged as a distinct class of proteins. For the tyrosine-based radical enzymes, we show that the spin-density distribution in the radical follows an odd alternate pattern that is invariant to within 10% across the class. General properties of the radical enzymes are summarized from which we conclude that their essential role in catalysis is to initiate substrate metabolism by hydrogen-atom abstraction. These ideas are extended to the Y-Z and Y-D tyrosines in Photosystem II and a radical-based hydrogen-atom abstraction model for water oxidation is discussed. Differences in rates of oxidation of Y-Z and Y-D by the reaction-center chlorophyll, P680(+), under various conditions, are considered and rationalized on the basis of changes in reorganization energy induced by the local protein structure and by the presence or absence of the (Mn)(4) cluster that binds substrate water.