Isolation and functional characterization of polyunsaturated fatty acid elongase (AsELOVL5) gene from black seabream (Acanthopagrus schlegelii)

To identify the genes encoding fatty acid elongases for the biosynthesis of polyunsaturated fatty acids (PUFAs), we isolated a cDNA via degenerate PCR and RACE-PCR from Acanthopagrus schlegelii with a high similarity to the ELOVL5-like elongases of mammals and fishes. This gene is termed AsELOVL5 and encodes a 294 amino acid protein. When AsELOVL5 was expressed in Saccharomyces cerevisiae, it conferred an ability to elongate gamma-linolenic acid (18:3 n-6) to di-homo-gamma-linolenic acid (20:3 n-6). In addition, the transformed cells converted arachidonic acid (20:4 n-6) and eicosapentaenpic acid (20:5 n-3) to docosatetraenoic acid (22:4 n-6) and docosapentaenoic acid (22:5 n-3), respectively. These results indicate that the AsELOVL5 gene encodes a long-chain fatty acid elongase capable of elongating C-18 Delta 6/C-20 Delta 5 but not C-22 PUFA substrates.