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.