PROBLEM TO BE SOLVED : To provide an enzyme and method of producing omega-3 fatty acid. SOLUTION : The method is for obtaining cells that can synthesize DPA and comprises : a) a step of introducing an exogenous polynucleotide that encodes a fatty acid elongase having Δ5 elongase activity that can be coupled so as to be activatable by a promoter that can induce the expression the polynucleotide in the cell; b) a step of expressing the exogenous polynucleotide in the cell; c) a step of analyzing the fatty acid composition in the cell; and d) a step of selecting cells in which Δ5 elongase produces DPA in cells selected at a rate of at least 60% and which is active with respect to EPA. SELECTED DRAWING : None COPYRIGHT : (C)2019, JPO&INPIT