Panasenko Oleg M, Vakhrusheva Tatyana, Tretyakov Vadim, Spalteholz Holger, Arnhold Juergen
Research Institute of Physico-Chemical Medicine, Malaya Pirogovskaya Street, 1a, Moscow 119992, Russia.
Chem Phys Lipids. 2007 Sep-Oct;149(1-2):40-51. doi: 10.1016/j.chemphyslip.2007.05.005. Epub 2007 May 18.
The leukocyte enzyme myeloperoxidase (MPO) is capable of catalyzing the oxidation of chloride and bromide ions, at physiological concentrations of these substrates, by hydrogen peroxide, generating hypochlorous acid (HOCl) and hypobromous acid (HOBr), respectively. Our previous results showed that the hypohalous acids formed react with double bonds in phosphatidylcholines (PCs) to produce chloro- and bromohydrins. Lysophosphatidylcholine (lyso-PC) is additionally formed in PCs with two or more double bonds. This study was conducted to determine the effect physiological chloride concentration (140 mM) has on the formation of bromohydrins and lyso-PC from unsaturated PC upon treatment with the myeloperoxidase/hydrogen peroxide/bromide (MPO/H2O2/Br-) system using physiological bromide concentrations (20-100 microM). The composition of reaction products was analyzed by matrix-assisted laser desorption and ionization time-of-flight mass spectrometry (MALDI-TOF MS). With monounsaturated PC, we demonstrated that the rate and extent of mono-bromohydrin formation were higher in the samples with 140 mM chloride compared to those with no added chloride. Moreover, mono-bromohydrin came to be the major product and no mono-chlorohydrin was observed already at 60 microM bromide. We attributed these effects to the involvement of HOBr arising from the reaction of MPO-derived HOCl with bromide rather than to the exchange of bromide with chlorine atoms of chlorohydrins or direct formation of HOBr by MPO. The presence of chloride shifted the pH optimum for mono-bromohydrin formation (pH 5.0) toward neutral values, and a significant yield of mono-bromohydrin was detected at physiological pH values (7.0-7.4). For polyunsaturated PC, chloride enhanced also lyso-PC production, the effect being pronounced at bromide concentrations below 40 microM. The results indicate that at physiological levels of chloride and bromide, chloride promotes MPO-mediated formation of bromohydrins and lyso-PC in unsaturated phospholipids.
白细胞酶髓过氧化物酶（MPO）能够在这些底物的生理浓度下，通过过氧化氢催化氯离子和溴离子的氧化，分别生成次氯酸（HOCl）和次溴酸（HOBr）。我们之前的结果表明，生成的次卤酸与磷脂酰胆碱（PC）中的双键反应生成氯代醇和溴代醇。在具有两个或更多双键的PC中还会额外生成溶血磷脂酰胆碱（lyso-PC）。本研究旨在确定生理浓度的氯离子（140 mM）在用髓过氧化物酶/过氧化氢/溴化物（MPO/H₂O₂/Br⁻）系统处理不饱和PC时，对溴代醇和lyso-PC形成的影响，该系统使用的是生理浓度的溴化物（20 - 100 μM）。通过基质辅助激光解吸电离飞行时间质谱（MALDI-TOF MS）分析反应产物的组成。对于单不饱和PC，我们证明，与未添加氯离子的样品相比，在含有140 mM氯离子的样品中，单溴代醇的形成速率和程度更高。此外，单溴代醇成为主要产物，并且在溴化物浓度为60 μM时就未观察到单氯代醇。我们将这些效应归因于MPO衍生的HOCl与溴化物反应产生的HOBr的参与，而不是溴化物与氯代醇的氯原子的交换或MPO直接形成HOBr。氯离子的存在使单溴代醇形成的最适pH值（pH 5.0）向中性值偏移，并且在生理pH值（7.0 - 7.4）下检测到显著产量的单溴代醇。对于多不饱和PC，氯离子也增强了lyso-PC的产生，在溴化物浓度低于40 μM时这种效应尤为明显。结果表明，在氯离子和溴化物的生理水平下，氯离子促进MPO介导的不饱和磷脂中溴代醇和lyso-PC的形成。
