Complete repertoire of long‐chain polyunsaturated fatty acids biosynthesis enzymes in a cyprinid, silver barb ( Barbonymus gonionotus ): Cloning, functional characterization and dietary regulation of Elovl2 and Elovl4

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.