1Department of Genetics and Genomic Sciences, Icahn Institute for Genomics and Multiscale Biology, Icahn School of Medicine at Mt. Sinai, 1425 Madison Ave., Box 1498, New York, NY 10029, USA.
FASEB J. 2014 Mar;28(3):1365-74. doi: 10.1096/fj.13-240416. Epub 2013 Dec 16.
Oxidation of unsaturated fatty acids requires the action of auxiliary enzymes, such as Δ(3),Δ(2)-enoyl-CoA isomerases. Here we describe a detailed biochemical, molecular, histological, and evolutionary characterization of Eci3, the fourth member of the mammalian enoyl-CoA isomerase family. Eci3 specifically evolved in rodents after gene duplication of Eci2. Eci3 is with 79% identity homologous to Eci2 and contains a peroxisomal targeting signal type 1. Subcellular fractionation of mouse kidney and immunofluorescence studies revealed a specific peroxisomal localization for Eci3. Expression studies showed that mouse Eci3 is almost exclusively expressed in kidney. By using immunohistochemistry, we found that Eci3 is not only expressed in cells of the proximal tubule, but also in a subset of cells in the tubulointerstitium and the glomerulus. In vitro, Eci3 catalyzed the isomerization of trans-3-nonenoyl-CoA to trans-2-nonenoyl-CoA equally efficient as Eci2, suggesting a role in oxidation of unsaturated fatty acids. However, in contrast to Eci2, in silico gene coexpression and enrichment analysis for Eci3 in kidney did not yield carboxylic acid metabolism, but diverse biological functions, such as ion transport (P=7.1E-3) and tissue morphogenesis (P=1.0E-3). Thus, Eci3 picked up a novel and unexpected role in kidney function during rodent evolution.
不饱和脂肪酸的氧化需要辅助酶的作用，如 Δ(3),Δ(2)-烯酰辅酶 A 异构酶。在这里，我们描述了哺乳动物烯酰辅酶 A 异构酶家族的第四个成员 Eci3 的详细生化、分子、组织学和进化特征。Eci3 是在 Eci2 基因复制后，专门在啮齿动物中进化而来的。Eci3 与 Eci2 具有 79%的同源性，并且包含一个过氧化物酶体靶向信号类型 1。鼠肾的亚细胞分级分离和免疫荧光研究显示 Eci3 具有特异性过氧化物酶体定位。表达研究表明，鼠 Eci3 几乎只在肾脏中表达。通过免疫组织化学，我们发现 Eci3 不仅在近端肾小管细胞中表达，而且在肾小管间质和肾小球中的一部分细胞中表达。在体外，Eci3 同样有效地催化反-3-壬烯酰辅酶 A 向反-2-壬烯酰辅酶 A 的异构化，表明其在不饱和脂肪酸的氧化中起作用。然而，与 Eci2 不同的是，Eci3 在肾脏中的基因共表达和富集分析在计算机上没有产生羧酸代谢，而是产生了多样化的生物学功能，如离子转运（P=7.1E-3）和组织形态发生（P=1.0E-3）。因此，Eci3 在啮齿动物进化过程中在肾脏功能中获得了一个新的、意想不到的作用。
