Mutation of a Critical Arginine in Microsomal Prostaglandin E Synthase-1 Shifts the Isomerase Activity to a Reductase Activity That Converts Prostaglandin H2 into Prostaglandin F2α
Mutation of a Critical Arginine in Microsomal Prostaglandin E Synthase-1 Shifts the Isomerase Activity to a Reductase Activity That Converts Prostaglandin H2 into Prostaglandin F2α
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DOI：
10.1074/jbc.m808365200
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发表时间：
2009-01-02
影响因子：
4.8
通讯作者：
Haeggstrom, Jesper Z.
中科院分区：
文献类型：
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作者：
Hammarberg, Tove;Hamberg, Mats;Haeggstrom, Jesper Z.
微粒体前列腺素E合成酶1(mPGES-1)通过环氧合酶将花生四烯酸产生的前列腺素内源性过氧化产物转化为前列腺素E-2。该酶属于二十烷类和谷胱甘肽代谢(MAPEG)家族中的膜相关蛋白，是一类完整的膜蛋白，由于其与炎症条件的联系以及与环氧合酶2的优先偶联，因此作为药物靶标受到了广泛的关注。基于人白三烯C-4合成酶的高分辨晶体结构，构建了一个mPGES-1模型，其中三肽共底物谷胱甘肽以马蹄形构象结合，其硫醇基团位于Arg-126附近。Arg-126突变为Ala或Gln会强烈降低该酶的前列腺素E合成酶活性(85-95%)，而邻近的Arg-122突变不会产生任何显著影响。有趣的是，R126A和R126Q mPGES-1显示了一种新的谷胱甘肽依赖的还原酶活性，它允许前列腺素H-2转化为前列腺素F-2α。我们的数据表明Arg-126是mPGES-1中的一个催化残基，表明MAPEG酶具有重要的活性部位结构成分。
Microsomal prostaglandin E synthase type 1 (mPGES-1) converts prostaglandin endoperoxides, generated from arachidonic acid by cyclooxygenases, into prostaglandin E-2. This enzyme belongs to the membrane-associated proteins in eicosanoid and glutathione metabolism (MAPEG) family of integral membrane proteins, and because of its link to inflammatory conditions and preferential coupling to cyclooxygenase 2, it has received considerable attention as a drug target. Based on the high resolution crystal structure of human leukotriene C-4 synthase, a model of mPGES-1 has been constructed in which the tripeptide co-substrate glutathione is bound in a horseshoe-shaped conformation with its thiol group positioned in close proximity to Arg-126. Mutation of Arg-126 into an Ala or Gln strongly reduces the enzyme's prostaglandin E synthase activity (85-95%), whereas mutation of a neighboring Arg-122 does not have any significant effect. Interestingly, R126A and R126Q mPGES-1 exhibit a novel, glutathione-dependent, reductase activity, which allows conversion of prostaglandin H-2 into prostaglandin F-2 alpha. Our data show that Arg-126 is a catalytic residue in mPGES-1 and suggest that MAPEG enzymes share significant structural components of their active sites.