Oboh Angela, Navarro Juan C, Tocher Douglas R, Monroig Oscar
Faculty of Natural Sciences, Institute of Aquaculture, University of Stirling, Stirling, FK9 4LA, Scotland, UK.
Department of Biological Sciences, University of Abuja, P.M.B. 117, Abuja, Nigeria.
Lipids. 2017 Oct;52(10):837-848. doi: 10.1007/s11745-017-4289-3. Epub 2017 Aug 30.
Elongation of very long-chain fatty acid 4 (Elovl4) proteins participate in the biosynthesis of very long-chain (>C) saturated and polyunsaturated fatty acids (FA). Previous studies have shown that fish possess two different forms of Elovl4, termed Elovl4a and Elovl4b. The present study aimed to characterize both molecularly and functionally two elovl4 cDNA from the African catfish Clarias gariepinus. The results confirmed that C. gariepinus possessed two elovl4-like elongases with high homology to two previously characterized Elovl4 from Danio rerio, and thus they were termed accordingly as Elovl4a and Elovl4b. The C. gariepinus Elovl4a and Elovl4b have open reading frames (ORF) of 945 and 915 base pairs, respectively, encoding putative proteins of 314 and 304 amino acids, respectively. Functional characterization in yeast showed both Elovl4 enzymes have activity towards all the PUFA substrates assayed (18:4n-3, 18:3n-6, 20:5n-3, 20:4n-6, 22:5n-3, 22:4n-6 and 22:6n-3), producing elongated products of up to C. Moreover, the C. gariepinus Elovl4a and Elovl4b were able to elongate very long-chain saturated FA (VLC-SFA) as denoted by increased levels of 28:0 and longer FA in yeast transformed with elovl4 ORF compared to control yeast. These results confirmed that C. gariepinus Elovl4 play important roles in the biosynthesis of very long-chain FA. Tissue distribution analysis of elovl4 mRNAs showed both genes were widely expressed in all tissues analyzed, with high expression of elovl4a in pituitary and brain, whereas female gonad and pituitary had the highest expression levels for elovl4b.
极长链脂肪酸延长酶4（Elovl4）蛋白参与极长链（>C）饱和脂肪酸和多不饱和脂肪酸（FA）的生物合成。先前的研究表明，鱼类拥有两种不同形式的Elovl4，分别称为Elovl4a和Elovl4b。本研究旨在从分子和功能上对来自非洲鲶鱼（Clarias gariepinus）的两种elovl4 cDNA进行表征。结果证实，非洲鲶鱼拥有两种与先前鉴定的来自斑马鱼（Danio rerio）的两种Elovl4具有高度同源性的elovl4样延长酶，因此它们被相应地命名为Elovl4a和Elovl4b。非洲鲶鱼Elovl4a和Elovl4b的开放阅读框（ORF）分别为945和915个碱基对，分别编码314和304个氨基酸的推定蛋白。在酵母中的功能表征表明，两种Elovl4酶对所有测定的多不饱和脂肪酸底物（18:4n-3、18:3n-6、20:5n-3、20:4n-6、22:5n-3、22:4n-6和22:6n-3）都有活性，产生长达C的延长产物。此外，与对照酵母相比，用elovl4开放阅读框转化的酵母中28:0和更长链脂肪酸水平的增加表明，非洲鲶鱼Elovl4a和Elovl4b能够延长极长链饱和脂肪酸（VLC-SFA）。这些结果证实，非洲鲶鱼Elovl4在极长链脂肪酸的生物合成中起重要作用。elovl4 mRNA的组织分布分析表明，这两个基因在所有分析的组织中都广泛表达，elovl4a在垂体和脑中高表达，而elovl4b在雌性性腺和垂体中的表达水平最高。
