The Enzyme Database

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EC 1.14.19.12     
Accepted name: acyl-lipid ω-(9-4) desaturase
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
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. [DOI] [PMID: 16267098]
[EC 1.14.19.12 created 2015]
 
 
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]
 
 
EC 1.14.19.47     
Accepted name: acyl-lipid (9-3)-desaturase
Reaction: (1) an α-linolenoyl-[glycerolipid] + 2 ferrocytochrome b5 + O2 + 2 H+ = a stearidonoyl-[glycerolipid] + ferricytochrome b5 + 2 H2O
(2) a linoleoyl-[glycerolipid] + 2 ferrocytochrome b5 + O2 + 2 H+ = a γ-linolenoyl-[glycerolipid] + ferricytochrome b5 + 2 H2O
Glossary: stearidonic acid = (6Z,9Z,12Z,15Z)-octadeca-6,9,12,15-tetraenoic acid
Other name(s): DES6 (gene name); acyl-lipid 6-desaturase; acyl-lipid Δ6-desaturase; Δ6-desaturase (ambiguous)
Systematic name: Δ9 acyl-[glycerolipid],ferrocytochrome b5:oxygen oxidoreductase (6,7-cis-dehydrogenating)
Comments: The enzyme, characterized from the moss Physcomitrella patens and the plant Borago officinalis (borage), introduces a cis double bond at carbon 6 of several acyl-lipids that contain an existing Δ9 cis double bond. The enzyme contains a cytochrome b5 domain that acts as the electron donor for the active site of the desaturase.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Sayanova, O., Smith, M.A., Lapinskas, P., Stobart, A.K., Dobson, G., Christie, W.W., Shewry, P.R. and Napier, J.A. Expression of a borage desaturase cDNA containing an N-terminal cytochrome b5 domain results in the accumulation of high levels of Δ6-desaturated fatty acids in transgenic tobacco. Proc. Natl. Acad. Sci. USA 94 (1997) 4211–4216. [DOI] [PMID: 9108131]
2.  Girke, T., Schmidt, H., Zähringer, U., Reski, R. and Heinz, E. Identification of a novel Δ6-acyl-group desaturase by targeted gene disruption in Physcomitrella patens. Plant J. 15 (1998) 39–48. [DOI] [PMID: 9744093]
[EC 1.14.19.47 created 2015]
 
 


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