摘要：The elongases of fatty acids (ELO) are essential for long chain polyunsaturated fatty acid (LC-PUFA) biosynthesis, and their activities depend on the substrates. The full length cDNA of Crassostrea angulata ELO (CaELO) was cloned by RACE PCR and its function was confirmed. The CaELO encodes a polypeptide of 309 amino acid residues, which containes a histidine box HXXHH motif conserved in all elongases and shares high similarity to the elongases of Chlamys nobilis and Octopus vulgaris. Phylogenetic analysis showed that the putative elongase was placed in the same group with ELOVL2 and ELOVL5, which have been demonstrated to be critical enzymes participating in the biosynthesis of PUFAs in vertebrates. When expressed in Saccharomyces cerevisiae, CaELO was able to elongate n-3 and n-6 PUFA substrates with chain lengths of C18 and C20, indicating that the CaELO had similar substrate specificities to vertebrate ELOVL5. CaELO had lower activity to elongate monounsaturated fatty acids, but had not activity to saturated fatty acids. Interestingly, the conversion rate of PUFAs depended on the length of carbon chain, the number of double bond, and n-3 / n-6 series in the species.
