Maroz Andrej, Anderson Robert F, Smith Robin A J, Murphy Michael P
Department of Chemistry, The University of Auckland, New Zealand.
Free Radic Biol Med. 2009 Jan 1;46(1):105-9. doi: 10.1016/j.freeradbiomed.2008.09.033. Epub 2008 Oct 14.
Endogenous ubiquinones (UQ) such as coenzyme Q(10) are essential electron carriers in the mitochondrial respiratory chain, and the reduced ubiquinol form (UQH(2)) is a chain-breaking antioxidant, decreasing oxidative damage caused by lipid peroxidation within mitochondria. Consequently, exogenous UQ are used as therapies to decrease mitochondrial oxidative damage. The proximal radical produced during mitochondrial oxidative stress is superoxide (O(2)(.-)) and the reaction between UQ and O(2)(.-) to form the ubisemiquinone radical anion (UQ(.-)) may also be important for the scavenging of O(2)(.-) by exogenous UQ. The situation in vivo is that many UQ are predominantly located in the hydrophobic membrane core, from which O(2)(.-) will be excluded but its conjugate acid, HOO(.), can enter. The reactivity of UQ or UQH(2) with HOO(.) has not been reported previously. Here a pulse radiolysis study on the reactions between UQ/UQH(2) and O(2)(.-)/HOO(.) in water and in solvent systems mimicking the surface and core of biological membranes has been undertaken. O(2)(.-) reacts very rapidly with UQ, suggesting that this may contribute to the scavenging of O(2)(.-) in vivo. In contrast, UQH(2) reacts relatively slowly with HOO(.), but rapidly with other oxygen- and carbon-centered radicals, indicating that the antioxidant role of UQH(2) is mainly in preventing lipid peroxidation.
内源性泛醌（UQ），如辅酶Q（10），是线粒体呼吸链中必不可少的电子载体，而还原型泛醇形式（UQH₂）是一种链断裂抗氧化剂，可减少线粒体内脂质过氧化引起的氧化损伤。因此，外源性泛醌被用作减少线粒体氧化损伤的疗法。线粒体氧化应激过程中产生的近端自由基是超氧阴离子（O₂⁻），泛醌与O₂⁻反应形成半醌自由基阴离子（UQ⁻）对外源性泛醌清除O₂⁻也可能很重要。体内的情况是，许多泛醌主要位于疏水膜核心，O₂⁻会被排除在外，但其共轭酸HOO·可以进入。此前尚未报道泛醌或泛醇（UQH₂）与HOO·的反应活性。在此，我们开展了一项脉冲辐解研究，研究泛醌/泛醇（UQ/UQH₂）与O₂⁻/HOO·在水以及模拟生物膜表面和核心的溶剂体系中的反应。O₂⁻与泛醌反应非常迅速，表明这可能有助于体内O₂⁻的清除。相比之下，泛醇（UQH₂）与HOO·反应相对较慢，但与其他以氧和碳为中心的自由基反应迅速，这表明泛醇（UQH₂）的抗氧化作用主要在于防止脂质过氧化。
