The silver barb (Barbonymus gonionotus) is a valuable cyprinid with good deposition of long‐chain polyunsaturated fatty acids (LC‐PUFA) such as docosahexaenoic acid (DHA). We have previously isolated a fatty acyl desaturase (Fads2) and elongase (Elovl5), which fulfils the production of eicosapentaenoic acid (EPA) and arachidonic acid (ARA) from C18 polyunsaturated fatty acid (PUFA) substrates. The isolation, functional characterization and dietary regulation of two elongases, Elovl2 and Elovl4, are reported here. The Elovl2 displayed the capacity to elongate C20 and C22 PUFA substrates, while the showed low activities towards saturated fatty acids and C22 PUFA substrates. This discovery validates the existence of a complete set of enzymes of LC‐PUFA in silver barb. The elovl2 showed higher expression in liver, in limited dietary LC‐PUFA intake conditions. As for Elovl4, tissue expression showed prominence in eye tissue. We also showed that the expression of both genes was upregulated when fish was fed with diets devoid of LC‐PUFA. Fatty acid composition analysis indicates the utilization of C18 polyunsaturated fatty acids for LC‐PUFA biosynthesis.

中文翻译：

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塞浦路斯，银倒钩（Barbonymus gonionotus）中长链多不饱和脂肪酸生物合成酶的完整清单：Elovl2和Elovl4的克隆，功能表征和饮食调节

银倒钩（Barbonymus gonionotus）是一种有价值的塞浦路斯，具有长链多不饱和脂肪酸（LC-PUFA）如二十二碳六烯酸（DHA）的良好沉积。我们以前已经分离出脂肪酰基去饱和酶（Fads2）和延伸酶（Elovl5），可实现从C18多不饱和脂肪酸（PUFA）底物生产二十碳五烯酸（EPA）和花生四烯酸（ARA）。此处报道了两种延长酶Elovl2和Elovl4的分离，功能表征和饮食调节。Elov12显示出拉长C20和C22 PUFA底物的能力，而显示出对饱和脂肪酸和C22 PUFA底物的低活性。这一发现证实了银倒钩中一整套LC-PUFA酶的存在。该ELOVL2在有限的饮食LC-PUFA摄入条件下显示肝脏中较高的表达。至于Elov14，组织表达在眼组织中突出。我们还表明，当用不含LC-PUFA的饲料喂养鱼时，这两个基因的表达均被上调。脂肪酸组成分析表明，利用C18多不饱和脂肪酸进行LC-PUFA生物合成。