Reaction: (1) a 1-γ-linolenoyl-2-acyl-[glycerolipid] + 2 reduced ferredoxin [iron-sulfur] cluster + O2 + 2 H+ = a 1-stearidonoyl-2-acyl-[glycerolipid] + 2 oxidized ferredoxin [iron-sulfur] cluster + 2 H2O
(2) a 1-linoleoyl-2-acyl-[glycerolipid] + 2 reduced ferredoxin [iron-sulfur] cluster + O2 + 2 H+ = a 1-α-linolenoyl-2-acyl-[glycerolipid] + 2 oxidized ferredoxin [iron-sulfur] cluster + 2 H2O
Glossary: stearidonic acid = (6Z,9Z,12Z,15Z)-octadeca-6,9,12,15-tetraenoic acid
Other name(s): desB (gene name)
Systematic name: 1-γ-linolenoyl-2-acyl-[glycerolipid],ferredoxin:oxygen oxidoreductase (15,16 cis-dehydrogenating)
Comments: The enzyme, characterized from cyanobacteria, introduces a cis double bond at carbon 15 of linoleoyl and γ-linolenoyl groups attached to the sn-1 position of glycerolipids. The enzyme is an ω desaturase, and determines the location of the double bond by counting three carbons from the methyl end of the fatty acid. It is nonspecific with respect to the polar head group of the glycerolipid. cf. EC 18.104.22.168, sn-2 acyl-lipid ω-3 desaturase (ferredoxin).
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:
1. Sakamoto, T., Los, D.A., Higashi, S., Wada, H., Nishida, I., Ohmori, M. and Murata, N. Cloning of ω3 desaturase from cyanobacteria and its use in altering the degree of membrane-lipid unsaturation. Plant Mol. Biol. 26 (1994) 249-263. [PMID: 7524725]