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.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:
References:
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]