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MetaCyc Enzyme: acyl-lipid ω-3 desaturase (endoplasmic reticulum)

Gene: FAD3 Accession Number: AT2G29980 (MetaCyc)

Synonyms: At2g29980, fatty acyl Δ15 desaturase (endoplasmic reticulum)

Species: Arabidopsis thaliana col

Subunit composition of acyl-lipid ω-3 desaturase (endoplasmic reticulum) = [FAD3]
         ω-3 fatty acid desaturase monomer = FAD3

Summary:
The FAD3 desaturase, which is located at the endoplasmic reticulum (ER), introduces a third double bond (Δ15) in linoleate incorporated into phosphatidylcholine, an important extra-plastidial membrane lipid, converting it into α-linolenate [Browse93].

The enzyme is an ω3 desaturase, which means it introduces the 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.

Like other desaturases located in the endoplasmic reticulum, the enzyme utilizes a cytochrome b5 as the electron donor [Ohlrogge95]. While the FAD3 gene does not include a cytochrome b5 domain, the enzyme uses cytochromes encoded by other genes. Higher plants contain multiple Cb5 genes, and it has been shown that certain Cb5 genes of Arabidopsis thaliana facilitate the accumulation of more desaturation products than others when co-expressed with FAD3 [Kumar12].

FAD3 was isolated by both map-based chromosome walking and T-DNA tagging. A cDNA clone was introduced into roots of both wild-type and mutant plants by Ti plasmid-mediated transformation, and transgenic tissues of both the mutant and wild-type plants had significantly increased amounts of the unsaturated fatty acids produced by this desaturase [Arondel92].

The ER desaturases FAD2 (18:1) and FAD3 (18:2) have been shown to act on fatty acids at both the sn-1 and sn-2 positions of phosphatidylcholine [Miquel92, Browse93]. It is possible that they act on other phospholipids as well, although this hasn't been verified [Ohlrogge95].

Locations: endoplasmic reticulum membrane, endoplasmic reticulum

Molecular Weight of Polypeptide: 44.077 kD (from nucleotide sequence)

Unification Links: ArrayExpress:P48623 , PhylomeDB:P48623 , Protein Model Portal:P48623 , String:P48623 , TAIR:AT2G29980 , UniProt:P48623

Relationship Links: InterPro:IN-FAMILY:IPR005804 , InterPro:IN-FAMILY:IPR021863 , Pfam:IN-FAMILY:PF00487 , Pfam:IN-FAMILY:PF11960

Gene-Reaction Schematic: ?

Gene-Reaction Schematic

GO Terms:

Cellular Component: GO:0005783 - endoplasmic reticulum
GO:0005789 - endoplasmic reticulum membrane

Credits:
Created 06-Aug-2008 by Caspi R , SRI International
Revised 11-Nov-2014 by Caspi R , SRI International


Enzymatic reaction of: ricinoleoyl-lipid 15-desaturase (acyl-lipid ω-3 desaturase (endoplasmic reticulum))

EC Number: 1.14.19.m

a [glycerolipid]-ricinoleate + 2 a ferrocytochrome b5 + oxygen + 2 H+ <=> a [glycerolipid]-densipolate + 2 a ferricytochrome b5 + 2 H2O

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.

The reaction is physiologically favored in the direction shown.


Enzymatic reaction of: linolenoyl-lipid 15-desaturase (acyl-lipid ω-3 desaturase (endoplasmic reticulum))

EC Number: 1.14.19.m

a [glycerolipid]-linoleate + 2 a ferrocytochrome b5 + oxygen + 2 H+ <=> a [glycerolipid]-α-linolenate + 2 a ferricytochrome b5 + 2 H2O

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.

The reaction is physiologically favored in the direction shown.

In Pathways: α-linolenate biosynthesis I (plants and red algae)


Enzymatic reaction of: 1-16:0-2-18:2-phosphatidylcholine desaturase (acyl-lipid ω-3 desaturase (endoplasmic reticulum))

EC Number: 1.14.19.m

1-palmitoyl-2-linoleoyl-phosphatidylcholine + 2 a ferrocytochrome b5 + oxygen + 2 H+ <=> 1-16:0-2-18:3-phosphatidylcholine + 2 a ferricytochrome b5 + 2 H2O

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.

The reaction is physiologically favored in the direction shown.

In Pathways: phospholipid desaturation


Enzymatic reaction of: 1-18:3-2-18:2-phosphatidylcholine desaturase (acyl-lipid ω-3 desaturase (endoplasmic reticulum))

EC Number: 1.14.19.m

1-18:3-2-18:2-phosphatidylcholine + 2 a ferrocytochrome b5 + oxygen + 2 H+ <=> 1-18:3-2-18:3-phosphatidylcholine + 2 a ferricytochrome b5 + 2 H2O

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.

The reaction is physiologically favored in the direction shown.

In Pathways: phospholipid desaturation


Enzymatic reaction of: 1-18:2-2-18:3-phosphatidylcholine desaturase (acyl-lipid ω-3 desaturase (endoplasmic reticulum))

EC Number: 1.14.19.m

1-18:2-2-18:3-phosphatidylcholine + 2 a ferrocytochrome b5 + oxygen + 2 H+ <=> 1-18:3-2-18:3-phosphatidylcholine + 2 a ferricytochrome b5 + 2 H2O

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.

The reaction is physiologically favored in the direction shown.

In Pathways: phospholipid desaturation


Enzymatic reaction of: 1-18:2-2-18:2-sn-glycerol-3-phosphocholine desaturase (acyl-lipid ω-3 desaturase (endoplasmic reticulum))

EC Number: 1.14.19.m

1-18:2-2-18:2-sn-glycerol-3-phosphocholine + 2 a ferrocytochrome b5 + oxygen + 2 H+ <=> 1-18:3-2-18:2-phosphatidylcholine + 2 a ferricytochrome b5 + 2 H2O

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.

The reaction is physiologically favored in the direction shown.

In Pathways: phospholipid desaturation


Enzymatic reaction of: 1-18:2-2-18:2-sn-glycerol-3-phosphocholine desaturase (acyl-lipid ω-3 desaturase (endoplasmic reticulum))

EC Number: 1.14.19.m

1-18:2-2-18:2-sn-glycerol-3-phosphocholine + 2 a ferrocytochrome b5 + oxygen + 2 H+ <=> 1-18:2-2-18:3-phosphatidylcholine + 2 a ferricytochrome b5 + 2 H2O

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.

The reaction is physiologically favored in the direction shown.

In Pathways: phospholipid desaturation


Enzymatic reaction of: 1-18:1-2-18:2-phosphatidylcholine desaturase (acyl-lipid ω-3 desaturase (endoplasmic reticulum))

EC Number: 1.14.19.m

1-18:1-2-18:2-phosphatidylcholine + 2 a ferrocytochrome b5 + oxygen + 2 H+ <=> 1-18:1-2-18:3-phosphatidylcholine + 2 a ferricytochrome b5 + 2 H2O

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.

The reaction is physiologically favored in the direction shown.

In Pathways: phospholipid desaturation


Enzymatic reaction of: 1-18:2-2-18:1-phosphatidylcholine desaturase (acyl-lipid ω-3 desaturase (endoplasmic reticulum))

EC Number: 1.14.19.m

1-18:2-2-18:1-phosphatidylcholine + 2 a ferrocytochrome b5 + oxygen + 2 H+ <=> 1-18:3-2-18:1-phosphatidylcholine + 2 a ferricytochrome b5 + 2 H2O

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.

The reaction is physiologically favored in the direction shown.

In Pathways: phospholipid desaturation


References

Arondel92: Arondel V, Lemieux B, Hwang I, Gibson S, Goodman HM, Somerville CR (1992). "Map-based cloning of a gene controlling omega-3 fatty acid desaturation in Arabidopsis." Science 258(5086);1353-5. PMID: 1455229

Broun97: Broun P, Somerville C (1997). "Accumulation of ricinoleic, lesquerolic, and densipolic acids in seeds of transgenic Arabidopsis plants that express a fatty acyl hydroxylase cDNA from castor bean." Plant Physiol 113(3);933-42. PMID: 9085577

Browse93: Browse J, McConn M, James D, Miquel M (1993). "Mutants of Arabidopsis deficient in the synthesis of alpha-linolenate. Biochemical and genetic characterization of the endoplasmic reticulum linoleoyl desaturase." J Biol Chem 1993;268(22);16345-51. PMID: 8102138

Kumar12: Kumar R, Tran LS, Neelakandan AK, Nguyen HT (2012). "Higher plant cytochrome b5 polypeptides modulate fatty acid desaturation." PLoS One 7(2);e31370. PMID: 22384013

Miquel92: Miquel M, Browse J (1992). "Arabidopsis mutants deficient in polyunsaturated fatty acid synthesis. Biochemical and genetic characterization of a plant oleoyl-phosphatidylcholine desaturase." J Biol Chem 267(3);1502-9. PMID: 1730697

Ohlrogge95: Ohlrogge J, Browse J (1995). "Lipid biosynthesis." Plant Cell 7(7);957-70. PMID: 7640528

Yadav93: Yadav NS, Wierzbicki A, Aegerter M, Caster CS, Perez-Grau L, Kinney AJ, Hitz WD, Booth JR, Schweiger B, Stecca KL (1993). "Cloning of higher plant omega-3 fatty acid desaturases." Plant Physiol 103(2);467-76. PMID: 8029334


Report Errors or Provide Feedback
Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
Page generated by SRI International Pathway Tools version 19.0 on Wed Sep 2, 2015, biocyc11.