SDD17 desaturase can convert arachidonic acid to eicosapentaenoic acid in mammalian cells

The possibility of elevating the omega-3 fatty acid contents in mammalian cells using the sdd17 gene from Saprolegnia diclina was investigated in the current study. The nucleotide sequence of the sdd17 gene was optimized and the pSDD17-IRES-GFP plasmid was introduced into murine 3T3 fibroblast cells by electroporation, following which its heterologous expression was evaluated by fatty acid analysis. Evaluation of GFP co-expression and RT-PCR analysis indicated that sdd17 could be expressed at very high levels in mammalian cells. Total cellular lipid analysis of transformed cells fed with arachidonic acid (20:4 n − 6) as a substrate showed that the sdd17 expression resulted in an 82-155% (p < 0.05) increase in eicosapentaenoic acid (20:5 n − 3) compared with the control. This expression also reduced the arachidonic acid/(eicosapentaenoic + docosapentaenoic + docosahexaenoic acid) ratio from approximately 4:1 in control cells to 1.5:1 in sdd17-transformed cells (p < 0.05). This study demonstrated that the foreign sdd17 gene from EPA-rich fungus was expressed at a high efficiency and caused the omega-3 fatty acid contents in mammalian cells to be elevated. It also provided a basis for potential applications of this gene in animal transgenesis.