Front-end desaturase having a omega-13 desaturase activity for omega-9 unsaturated C18/C20 fatty acids. Strong substrate preferences for linoleic acid and alpha-linolenic acid for the production of pinolenic and coniferonic acids respectively. No desaturase activity for dihomo gamma-linolenic acid and eicosatertraenoic acid. a (9Z,12Z)-octadecadienoyl-containing glycerolipid + 2 Fe(II)-[cytochrome b5] + 2 H(+) + O2 = a (5Z,9Z,12Z)-octadecatrienoyl-containing glycerolipid + 2 Fe(III)-[cytochrome b5] + 2 H2O (9Z,12Z,15Z)-octadecatrienoyl-containing glycerolipid + 2 Fe(II)-[cytochrome b5] + 2 H(+) + O2 = a (5Z,9Z,12Z,15Z)-octadecatetraenoyl-containing glycerolipid + 2 Fe(III)-[cytochrome b5] + 2 H2O Lipid metabolism; polyunsaturated fatty acid biosynthesis. The histidine box domains may contain the active site and/or be involved in metal ion binding. Belongs to the fatty acid desaturase type 1 family.