Reaction: a linoleoyl-[glycerolipid] + 2 ferrocytochrome b5 + O2 + 2 H+ = an α-linolenoyl-[glycerolipid] + 2 ferricytochrome b5 + 2 H2O
Glossary: linoleoyl-[glycerolipid] = (9Z,12Z)-octadeca-9,12-dienoyl-[glycerolipid]
α-linolenoyl-[glycerolipid] = (9Z,12Z,15Z)-octadeca-9,12,15-trienoyl-[glycerolipid]
Other name(s): FAD3
Systematic name: (9Z,12Z)-octadeca-9,12-dienoyl-[glycerolipid],ferrocytochrome b5:oxygen oxidoreductase (15,16 cis-dehydrogenating)
Comments: This microsomal enzyme introduces a cis double bond three carbons away from the methyl end of a fatty acid incorporated into a glycerolipid. The distance from the carboxylic acid end of the molecule does not have an effect. The plant enzyme acts on carbon 15 of linoleoyl groups incorporated into both the sn-1 and sn-2 positions of the glycerol backbone of phosphatidylcholine and other phospholipids, converting them into α-linolenoyl groups. The enzyme from the fungus Mortierella alpina acts on γ-linolenoyl and arachidonoyl groups, converting them into stearidonoyl and icosapentaenoyl groups, respectively [3]. cf. EC 1.14.19.35, acyl-lipid ω-3 desaturase (ferredoxin).
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:
References:
1. Browse, J., McConn, M., James, D., Jr. and Miquel, M. Mutants of Arabidopsis deficient in the synthesis of α-linolenate. Biochemical and genetic characterization of the endoplasmic reticulum linoleoyl desaturase. J. Biol. Chem. 268 (1993) 16345-16351. [PMID: 8102138]
2. Arondel, V., Lemieux, B., Hwang, I., Gibson, S., Goodman, H.M. and Somerville, C.R. Map-based cloning of a gene controlling ω-3 fatty acid desaturation in Arabidopsis. Science 258 (1992) 1353-1355. [PMID: 1455229]
3. Sakuradani, E., Abe, T., Iguchi, K. and Shimizu, S. A novel fungal ω3-desaturase with wide substrate specificity from arachidonic acid-producing Mortierella alpina 1S-4. Appl. Microbiol. Biotechnol. 66 (2005) 648-654. [PMID: 15538555]