The Enzyme Database

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EC 1.14.19.25     
Accepted name: acyl-lipid ω-3 desaturase (cytochrome b5)
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, sn-2 acyl-lipid ω-3 desaturase (ferredoxin).
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
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. [DOI] [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. [DOI] [PMID: 15538555]
[EC 1.14.19.25 created 2015]
 
 
EC 1.14.19.35     
Accepted name: sn-2 acyl-lipid ω-3 desaturase (ferredoxin)
Reaction: (1) a (7Z,10Z)-hexadeca-7,10-dienoyl-[glycerolipid] + 2 reduced ferredoxin [iron-sulfur] cluster + O2 + 2 H+ = a (7Z,10Z,13Z)-hexadeca-7,10,13-trienoyl-[glycerolipid] + 2 oxidized ferredoxin [iron-sulfur] cluster + 2 H2O
(2) a linoleoyl-[glycerolipid] + 2 reduced ferredoxin [iron-sulfur] cluster + O2 + 2 H+ = an α-linolenoyl-[glycerolipid] + 2 oxidized ferredoxin [iron-sulfur] cluster + 2 H2O
Glossary: (9Z,12Z)-octadeca-9,12-dienoyl-[glycerolipid] = linoleoyl-[glycerolipid]
(9Z,12Z,15Z)-octadeca-9,12,15-trienoyl-[glycerolipid] = α-linolenoyl-[glycerolipid]
Other name(s): FAD7; FAD8
Systematic name: (7Z,10Z)-hexadeca-7,10-dienoyl-[glycerolipid],ferredoxin:oxygen oxidoreductase (13,14 cis-dehydrogenating)
Comments: This plastidial enzyme desaturates 16:2 fatty acids attached to the sn-2 position of glycerolipids to 16:3 fatty acids, and converts18:2 to 18:3 in both the sn-1 and sn-2 positions. It acts on all 16:2- or 18:2-containing chloroplast membrane lipids, including phosphatidylglycerol, monogalactosyldiacylglycerol, digalactosyldiaclyglycerol, and sulfoquinovosyldiacylglycerol. The enzyme introduces a cis double bond at a location 3 carbons away from the methyl end of the fatty acid. The distance from the carboxylic acid end of the molecule does not affect the location of the new double bond. cf. EC 1.14.19.25, acyl-lipid ω-3 desaturase (cytochrome b5) and EC 1.14.19.36, sn-1 acyl-lipid ω-3 desaturase (ferredoxin).
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Iba, K., Gibson, S., Nishiuchi, T., Fuse, T., Nishimura, M., Arondel, V., Hugly, S. and Somerville, C. A gene encoding a chloroplast ω-3 fatty acid desaturase complements alterations in fatty acid desaturation and chloroplast copy number of the fad7 mutant of Arabidopsis thaliana. J. Biol. Chem. 268 (1993) 24099–24105. [PMID: 8226956]
2.  McConn, M., Hugly, S., Browse, J. and Somerville, C. A mutation at the fad8 locus of Arabidopsis identifies a second chloroplast ω-3 desaturase. Plant Physiol. 106 (1994) 1609–1614. [PMID: 12232435]
3.  Venegas-Caleron, M., Muro-Pastor, A.M., Garces, R. and Martinez-Force, E. Functional characterization of a plastidial ω-3 desaturase from sunflower (Helianthus annuus) in cyanobacteria. Plant Physiol. Biochem. 44 (2006) 517–525. [DOI] [PMID: 17064923]
[EC 1.14.19.35 created 2015]
 
 


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