The Precise Structures and Stereochemistry of Trihydroxy-linoleates Esterified in Human and Porcine Epidermis and Their Significance in Skin Barrier Function: IMPLICATION OF AN EPOXIDE HYDROLASE IN THE TRANSFORMATIONS OF LINOLEATE.
The Precise Structures and Stereochemistry of Trihydroxy-linoleates Esterified in Human and Porcine Epidermis and Their Significance in Skin Barrier Function: IMPLICATION OF AN EPOXIDE HYDROLASE IN THE TRANSFORMATIONS OF LINOLEATE.
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DOI：
10.1074/jbc.m115.711267
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发表时间：
2016-07-08
期刊：
影响因子：
--
通讯作者：
Brash AR
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文献类型：
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作者：
Chiba T;Thomas CP;Calcutt MW;Boeglin WE;O'Donnell VB;Brash AR
在干燥的陆地上生存的先决条件是，要形成完整的皮肤水屏障，就需要脂氧化酶催化必需脂肪酸亚油酸的氧化，亚油酸被酯化成表皮特异性神经酰胺的ω-羟基。脂氧合酶氧化亚油酸部分促进酯键的酶切，释放游离的ω-羟基神经酰胺与蛋白质共价结合，从而形成角质细胞脂质包膜，这是表皮屏障的关键组成部分。在这里，我们报道了酯化亚油酸酯的转化超越了氧化和环氧醇合成的初始步骤，由12R-LOX和表皮LOX3的连续作用催化。人类和猪表皮的主要最终产物是一种三羟基衍生物，其形成的特异性意味着环氧化物水解酶参与了环氧醇转化为三醇的过程。在9,10-环氧-13-羟基十八烯酸酯水解产生的16种可能的三醇中，使用LC-MS和手性分析，我们特异性地鉴定和量化了9R，10S， 13r -三羟基- 11e -十八烯酸酯作为猪表皮中酯化的单一主要三醇，以及在人表皮中具有较少数量的10R非对映体的相同异构体。9R,10S， 13r -三醇是由LOX酶的9R， 10r -环氧- 13r -羟基十八烯酸盐产物SN2水解形成的，这是环氧化物水解酶的反应特异性特征。三醇在初级亚油酸产品上的高极性增强了氧化破坏角质层膜脂的概念，促进自由ω-羟基神经酰胺的释放，用于与蛋白质的共价结合和防水屏障的密封。
Creation of an intact skin water barrier, a prerequisite for life on dry land, requires the lipoxygenase-catalyzed oxidation of the essential fatty acid linoleate, which is esterified to the ω-hydroxyl of an epidermis-specific ceramide. Oxidation of the linoleate moiety by lipoxygenases is proposed to facilitate enzymatic cleavage of the ester bond, releasing free ω-hydroxyceramide for covalent binding to protein, thus forming the corneocyte lipid envelope, a key component of the epidermal barrier. Herein, we report the transformations of esterified linoleate proceed beyond the initial steps of oxidation and epoxyalcohol synthesis catalyzed by the consecutive actions of 12R-LOX and epidermal LOX3. The major end product in human and porcine epidermis is a trihydroxy derivative, formed with a specificity that implicates participation of an epoxide hydrolase in converting epoxyalcohol to triol. Of the 16 possible triols arising from hydrolysis of 9,10-epoxy-13-hydroxy-octadecenoates, using LC-MS and chiral analyses, we identify and quantify specifically 9R,10S,13R-trihydroxy-11E-octadecenoate as the single major triol esterified in porcine epidermis and the same isomer with lesser amounts of its 10R diastereomer in human epidermis. The 9R,10S,13R-triol is formed by SN2 hydrolysis of the 9R,10R-epoxy-13R-hydroxy-octadecenoate product of the LOX enzymes, a reaction specificity characteristic of epoxide hydrolase. The high polarity of triol over the primary linoleate products enhances the concept that the oxidations disrupt corneocyte membrane lipids, promoting release of free ω-hydroxyceramide for covalent binding to protein and sealing of the waterproof barrier.