Reaction: an oleoyl-[glycerolipid] + 2 reduced ferredoxin [iron-sulfur] cluster + O2 + 2 H+ = a linoleoyl-[glycerolipid] + 2 oxidized ferredoxin [iron-sulfur] cluster + 2 H2O
Other name(s): acyl-lipid ω6-desaturase (ferredoxin); oleate desaturase (ambiguous); linoleate synthase (ambiguous); oleoyl-CoA desaturase (ambiguous); oleoylphosphatidylcholine desaturase (ambiguous); phosphatidylcholine desaturase (ambiguous); FAD6 (gene name)
Systematic name: oleoyl-[glycerolipid],ferredoxin:oxygen oxidoreductase (12,13 cis-dehydrogenating)
Comments: This plastidial enzyme is able to insert a cis double bond in monounsaturated fatty acids incorporated into glycerolipids. The enzyme introduces the new bond at a position 3 carbons away from the existing double bond, towards the methyl end of the fatty acid. The native substrates are oleoyl (18:1 Δ9) and (Z)-hexadec-7-enoyl (16:1 Δ7) groups attached to either position of the glycerol backbone in glycerolipids, resulting in the introduction of the second double bond at positions 12 and 10, respectively This prompted the suggestion that this is an ω6 desaturase. However, when acting on palmitoleoyl groups(16:1 Δ9), the enzyme introduces the second double bond at position 12 (ω4), indicating it is an (n+3) desaturase [3]. cf. EC 1.14.19.34, acyl-lipid (9+3)-(E)-desaturase.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:
References:
1. Schmidt, H. and Heinz, E. Desaturation of oleoyl groups in envelope membranes from spinach chloroplasts. Proc. Natl. Acad. Sci. USA 87 (1990) 9477-9480. [PMID: 11607123]
2. Schmidt, H. and Heinz, E. Involvement of ferredoxin in desaturation of lipid-bound oleate in chloroplasts. Plant Physiol. 94 (1990) 214-220. [PMID: 16667689]
3. Hitz, W.D., Carlson, T.J., Booth, J.R., Jr., Kinney, A.J., Stecca, K.L. and Yadav, N.S. Cloning of a higher-plant plastid ω-6 fatty acid desaturase cDNA and its expression in a cyanobacterium. Plant Physiol. 105 (1994) 635-641. [PMID: 8066133]
4. Falcone, D.L., Gibson, S., Lemieux, B. and Somerville, C. Identification of a gene that complements an Arabidopsis mutant deficient in chloroplast ω 6 desaturase activity. Plant Physiol. 106 (1994) 1453-1459. [PMID: 7846158]
5. Schmidt, H., Dresselhaus, T., Buck, F. and Heinz, E. Purification and PCR-based cDNA cloning of a plastidial n-6 desaturase. Plant Mol. Biol. 26 (1994) 631-642. [PMID: 7948918]