Identification of Δ9-Elongation Activity from Thraustochytrium aureum by Heterologous Expression in Pichia pastoris

The Delta 9-elongase isolated from Thraustochytrium aureum, which contains a high level of polyunsaturated fatty acids (PUFAs), was demonstrated to be associated with the synthesis of C20 PUFAs. The TaELO gene contains a 825 bp ORF that encodes a protein of 274 amino acids that shares a high similarity with other PUFA elongases. The expression of the TaELO gene in Pichia pastoris resulted in the elongation of linoleic acid (LA, C18:2; n-6) and (x-linolenic acid (ALA, C18:3; n-3) to eicosadienoic acid (EDA, C20:2; n-6) and eicosatrienoic acid (ETrA, C20:3; n-3), respectively. The endogenous conversion rate of LA and ALA to EDA and ETrA was 32.68 and 38.57%, respectively. In addition, TaELO was also able to synthesize eicosenoic acid (C20:1; n-9) from oleic acid (OA, C18:1; n-9), even though the conversion level was low (2.81%). Furthermore, TaELO was able to carry out the Delta 6-elongation of gamma-linolenic acid (GLA, C18:3; n-6) to dihomo-gamma-linolenic acid (DGLA, C20:3; n-6) and Delta 5-elongation of eicosapentaenoic acid (EPA, C20:5; n-3) to docosapentaenoic acid (DPA, C22:5; n-3). The conversion rate of GLA to DGLA and EPA to DPA were 93 and 28.36%, respectively. The TaELO protein was confirmed to have multifunctional activities, such as Delta 9, Delta 6, and Delta 5-elongations as well as the elongation of monounsaturated fatty acid. (C) KSBB