Fatty acid acetylenase able to introduce a delta(6)-triple bond into gamma-linolenic and stearidonic acid. Also able to introduce a delta(6)-double bond into delta(9)-unsaturated fatty-acid substrates. (6Z,9Z,12Z)-octadecatrienoyl-containing glycerolipid + 2 Fe(II)-[cytochrome b5] + 2 H(+) + O2 = a (9Z,12Z)-octadeca-9,12-dien-6-ynoyl-containing glycerolipid + 2 Fe(III)-[cytochrome b5] + 2 H2O (6Z,9Z,12Z,15Z)-octadecatetraenoyl-containing glycerolipid + 2 Fe(II)-[cytochrome b5] + 2 H(+) + O2 = a (9Z,12Z,15Z)-octadeca-9,12,15-trien-6-ynoyl-containing glycerolipid + 2 Fe(III)-[cytochrome b5] + 2 H2O (9Z,12Z,15Z)-octadecatrienoyl-containing glycerolipid + 2 Fe(II)-[cytochrome b5] + 2 H(+) + O2 = (6Z,9Z,12Z,15Z)-octadecatetraenoyl-containing glycerolipid + 2 Fe(III)-[cytochrome b5] + 2 H2O a (9Z,12Z)-octadecadienoyl-containing glycerolipid + 2 Fe(II)-[cytochrome b5] + 2 H(+) + O2 = (6Z,9Z,12Z)-octadecatrienoyl-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.