preferred_name: an (8Z,11Z,14Z,17Z)-eicosatetraenoyl-containing glycerolipid + 2 Fe(II)-[cytochrome b5] + O2 + 2 H(+) <=> a (5Z,8Z,11Z,14Z,17Z)-eicosapentaenoyl-containing glycerolipid + 2 Fe(III)-[cytochrome b5] + 2 H2O