Yu Zheyong, Schneider Claus, Boeglin William E, Brash Alan R
Department of Pharmacology, Vanderbilt University School of Medicine, 23rd Ave. at Pierce, Nashville, TN 37232-6602, USA.
Biochim Biophys Acta. 2005 Jan 5;1686(3):238-47. doi: 10.1016/j.bbalip.2004.10.007.
Non-bullous congenital ichthyosiform erythroderma (NCIE) is one of the main clinical forms of ichthyosis. Genetic studies indicated that 12R-lipoxygenase (12R-LOX) or epidermal lipoxygenase-3 (eLOX3) was mutated in six families affected by NCIE [F. Jobard, C. Lefevre, A. Karaduman, C. Blanchet-Bardon, S. Emre, J. Weissenbach, M. Ozguc, M. Lathrop, J.F. Prud'homme, J. Fischer, Lipoxygenase-3 (ALOXE3) and 12(R)-lipoxygenase (ALOX12B) are mutated in non-bullous congenital ichthyosiform erythroderma (NCIE) linked to chromosome 17p13.1, Hum. Mol. Genet. 11 (2002) 107-113.], but the impact of these mutations on LOX function has not been defined. To explore this, we overexpressed the wild-type or mutated enzymes in E. coli and COS7 cells and then analyzed the essential catalytic properties. We showed recently that human eLOX3 is a hydroperoxide isomerase (hepoxilin synthase) that converts the product of 12R-LOX, 12R-hydroperoxyeicosatetraenoic acid (12R-HPETE) to a specific epoxyalcohol. Using incubations with [(14)C]-labeled substrates and HPLC analyses, we found that the naturally occurring mutations totally eliminate the lipoxygenase activity of 12R-LOX and the hydroperoxide isomerase activity of eLOX3. We further demonstrate that the 12R-LOX/eLOX3-derived 8R-hydroxy-11R,12R-epoxide is converted by an epoxide hydrolase in COS7 cells and in human keratinocytes to a single isomer of 8,11,12-trihydroxyeicosa-5,9,14-trienoic acid. Taken together, the results support the hypothesis that 12R-LOX, eLOX3, and perhaps an epoxide hydrolase function together in the normal process of skin differentiation, and that the loss of function mutations are the basis of the LOX-dependent form of NCIE.
非大疱性先天性鱼鳞病样红皮病（NCIE）是鱼鳞病的主要临床类型之一。基因研究表明，在6个受NCIE影响的家族中，12R-脂氧合酶（12R-LOX）或表皮脂氧合酶-3（eLOX3）发生了突变[F. 乔巴德、C. 勒费弗尔、A. 卡拉杜曼、C. 布兰切特-巴登、S. 埃姆雷、J. 魏森巴赫、M. 奥兹古克、M. 拉思罗普、J.F. 普鲁德'homme、J. 菲舍尔，脂氧合酶-3（ALOXE3）和12（R）-脂氧合酶（ALOX12B）在与17p13.1染色体连锁的非大疱性先天性鱼鳞病样红皮病（NCIE）中发生突变，《人类分子遗传学》11（2002）107 - 113]，但这些突变对脂氧合酶功能的影响尚未明确。为了探究这一点，我们在大肠杆菌和COS7细胞中过表达野生型或突变型酶，然后分析其基本催化特性。我们最近表明，人eLOX3是一种氢过氧化物异构酶（hepoxilin合酶），可将产物12R-LOX的12R-氢过氧化二十碳四烯酸（12R-HPETE）转化为一种特定的环氧醇。通过用[（14）C]标记的底物进行孵育和高效液相色谱分析，我们发现自然发生的突变完全消除了12R-LOX的脂氧合酶活性和eLOX3的氢过氧化物异构酶活性。我们进一步证明，在COS7细胞和人角质形成细胞中，由12R-LOX/eLOX3衍生的8R-羟基-11R，12R-环氧化物被一种环氧水解酶转化为8，11，12-三羟基二十碳-5，9，14-三烯酸的单一异构体。综上所述，这些结果支持以下假设：12R-LOX、eLOX3以及可能的一种环氧水解酶在皮肤正常分化过程中共同发挥作用，并且功能丧失性突变是NCIE的脂氧合酶依赖性形式的基础。
