Plasmanylethanolamine desaturase involved in plasmalogen biogenesis in the endoplasmic reticulum membrane. Plasmalogens are glycerophospholipids with a hydrocarbon chain linked by a vinyl ether bond at the glycerol sn-1 position, and are involved in antioxidative and signaling mechanisms. 1-(1,2-saturated alkyl)-2-acyl-sn-glycero-3-phosphoethanolamine + 2 Fe(II)-[cytochrome b5] + 2 H(+) + O2 = 1-O-(1Z-alkenyl)-2-acyl-sn-glycero-3-phosphoethanolamine + 2 Fe(III)-[cytochrome b5] + 2 H2O a 1-O-hexadecyl-2-acyl-sn-glycero-3-phosphoethanolamine + 2 Fe(II)-[cytochrome b5] + 2 H(+) + O2 = a 1-O-(1Z-hexadecenyl)-2-acyl-sn-glycero-3-phosphoethanolamine + 2 Fe(III)-[cytochrome b5] + 2 H2O a 1-O-octadecyl-2-acyl-sn-glycero-3-phosphoethanolamine + 2 Fe(II)-[cytochrome b5] + 2 H(+) + O2 = a 1-O-(1Z-octadecenyl)-2-acyl-sn-glycero-3-phosphoethanolamine + 2 Fe(III)-[cytochrome b5] + 2 H2O a 1-O-(9Z-octadecenyl)-2-acyl-sn-glycero-3-phosphoethanolamine + 2 Fe(II)-[cytochrome b5] + 2 H(+) + O2 = a 1-O-(1Z,9Z-octadecadienyl)-2-acyl-sn-glycero-3-phosphoethanolamine + 2 Fe(III)-[cytochrome b5] + 2 H2O Lipid metabolism; fatty acid metabolism. Histidine box-1 and -2 together with other histidine residues are essential for catalytic activity. Body weight is reduced in homozygous deficient male and female. Deficient mice lack plasmanylethanolamine desaturase activity and have dramatically lowered plasmalogen levels in their tissues. Belongs to the fatty acid desaturase CarF family.