Fatty acid conjugase converting 18:2(9Z, 12Z) to calendic acid 18:3(8E, 10E, 12Z) (PubMed:11067856, PubMed:11161042, PubMed:12383261). Converts alpha-linolenic acid (18:3(9Z, 12Z, 15Z)) into 18:4(8E, 10E, 12Z, 15Z) (PubMed:11067856). Also has weak activity on the mono-unsaturates 16:1(9Z) and 18:1(9Z) producing two conjugated double bonds at delta(8) and delta(10) position (PubMed:11161042). a (9Z,12Z)-octadecadienoyl-containing glycerolipid + AH2 + O2 = A + a (8E,10E,12Z)-octadecatrienoyl-containing glycerolipid + 2 H2O Lipid metabolism; polyunsaturated fatty acid biosynthesis. Expressed exclusively in the developing seeds. Not detected in leaves or flower buds. 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.