The enzyme, characterized from the green alga Chlamydomonas reinhardtii, is a front-end desaturase that introduces a cis double bond in ¦Ø9 unsaturated C18 or C20 fatty acids incorporated into lipids, at a position 4 carbon atoms from the existing ¦Ø9 bond, towards the carboxy end of the fatty acid (at the ¦Ø13 position). When acting on 20:2¦¤(11,14) and 20:3¦¤(11,14,17) substrates it introduces the new double bond between carbons 7 and 8. The enzyme contains a cytochrome b5 domain that acts as the direct electron donor for the active site of the desaturase.
