Catalyzes the desaturation of 20:2Delta(11,14) and 20:3Delta(11,14,17) to generate sciadonic acid (20:3Delta(5,11,14)) and juniperonic acid (20:4Delta(5,11,14,17)). (11Z,14Z)-eicosadienoyl-CoA + AH2 + O2 = (5Z,11Z,14Z)-eicosatrienoyl-CoA + A + 2 H2O (11Z,14Z,17Z)-eicosatrienoyl-CoA + AH2 + O2 = (5Z,11Z,14Z,17Z)-eicosatetraenoyl-CoA + A + 2 H2O Expected to bind 2 Fe(2+) ions per subunit. Lipid metabolism; polyunsaturated fatty acid biosynthesis. The histidine box domains are involved in binding the catalytic metal ions. Belongs to the fatty acid desaturase type 1 family.