Accepted name: acyl-lipid ω-(9-4) desaturase
Reaction: (1) linoleoyl-[glycerolipid] + 2 ferrocytochrome b5 + O2 + 2 H+ = pinolenoyl-[glycerolipid] + 2 ferricytochrome b5 + 2 H2O
(2) α-linolenoyl-[glycerolipid] + 2 ferrocytochrome b5 + O2 + 2 H+ = coniferonoyl-[glycerolipid] + 2 ferricytochrome b5 + 2 H2O
Glossary: taxoleate = (5Z,9Z)-octadeca-5,9-dienoate
pinolenoate = (5Z,9Z,12Z)-octadeca-5,9,12-trienoate
coniferonate = (5Z,9Z,12Z,15Z)-octadeca-5,9,12,15-tetraenoate
Other name(s): acyl-lipid ω-13 desaturase; acyl-lipid 7-desaturase (ambiguous)
Systematic name: acyl-[glycerolipid],ferrocytochrome b5:oxygen oxidoreductase [ω(9-4),ω(9-5) cis-dehydrogenating]
Comments: The enzyme, characterized from the green alga Chlamydomonas reinhardtii, is a front-end desaturase that introduces a cis double bond in ω9 unsaturated C18 or C20 fatty acids incorporated into lipids, at a position 4 carbon atoms from the existing ω9 bond, towards the carboxy end of the fatty acid (at the ω13 position). When acting on 20:2Δ(11,14) and 20:3Δ(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.
1.  Kajikawa, M., Yamato, K.T., Kohzu, Y., Shoji, S., Matsui, K., Tanaka, Y., Sakai, Y. and Fukuzawa, H. A front-end desaturase from Chlamydomonas reinhardtii produces pinolenic and coniferonic acids by ω13 desaturation in methylotrophic yeast and tobacco. Plant Cell Physiol. 47 (2006) 64–73. [PMID: 16267098]
[EC created 2015]