Lipoxygenase reaction mechanism: Demonstration that hydrogen abstraction from substrate precedes dioxygen binding during catalytic turnover
Lipoxygenase reaction mechanism: Demonstration that hydrogen abstraction from substrate precedes dioxygen binding during catalytic turnover
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DOI：
10.1021/bi960985q
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发表时间：
1996-10-01
期刊：
影响因子：
2.9
通讯作者：
Klinman, JP
中科院分区：
文献类型：
--
作者：
Glickman, MH;Klinman, JP
由于自旋守恒规则，分子氧通常对共价键不起反应;因此，利用氧的酶的主要作用是通过电子构型的变化来激活双氧。为了了解脂氧合酶在催化周转条件下如何催化脂质氢过氧化，已测量了氘同位素动力学效应作为氧浓度的函数。氧与脂氧合酶结合的性质也一直在研究中。本文所呈现的结果表明，在稳态条件下，大气中的氧进入反应途径后，从基板的氢提取。此外，还不可能检测到在没有活化底物的情况下能够结合分子氧的任何形式的脂氧合酶。我们提出，分子氧是不生产性地绑定由脂氧合酶，而是直接与底物自由基脂氧合酶相互作用，形成亚油酸的氢过氧自由基，涉及底物活化的机制，而不是更熟悉的氧活化途径，是一个独特的机制，金属加氧酶。
Molecular oxygen is generally unreactive toward covalent bonds, due to spin conservation rules; a major role for oxygen-utilizing enzymes is, therefore, to activate dioxygen through a change in electronic configuration. In an effort to understand how lipoxygenase catalyzes lipid hydroperoxidation under conditions of catalytic turnover, kinetic deuterium isotope effects have been measured as a function of oxygen concentration. The properties of oxygen binding to lipoxygenase have also been pursued. The results presented herein show that, under steady state conditions, atmospheric oxygen enters the reaction pathway only after abstraction of hydrogen from substrate. Furthermore, it has not been possible to detect any form of lipoxygenase capable of binding molecular oxygen in the absence of activated substrate. We propose that molecular oxygen is not productively bound by lipoxygenase but rather interacts directly with the substrate radical Lipoxygenase to form the hydroperoxyl radical of linoleate, A mechanism involving substrate activation, instead of the more familiar oxygen activation pathway, is a unique mechanism for a metallo-oxygenase.