Updated BioCyc iOS App now
available in iTunes store
Updated BioCyc iOS App now
available in iTunes store
Updated BioCyc iOS App now
available in iTunes store
Updated BioCyc iOS App now
available in iTunes store
Updated BioCyc iOS App now
available in iTunes store

MetaCyc Pathway: arachidonate biosynthesis I (6-desaturase, lower eukaryotes)
Inferred from experiment

Enzyme View:

Pathway diagram: arachidonate biosynthesis I (6-desaturase, lower eukaryotes)

This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.

Synonyms: arachidonic acid biosynthesis I (lower eukaryotes)

Superclasses: BiosynthesisFatty Acid and Lipid BiosynthesisFatty Acid BiosynthesisUnsaturated Fatty Acid BiosynthesisPolyunsaturated Fatty Acid BiosynthesisArachidonate Biosynthesis

Some taxa known to possess this pathway include : Mortierella alpina, Physcomitrella patens

Expected Taxonomic Range: Bryophyta , Chlorophyta, Fungi

General Background

Long-chain polyunsaturated fatty acids (PUFAs) are fatty acid that have 13 or more carbon atoms and contain more than one double bond in their backbone. The PUFAs that have 2 or more cis double bonds separated from each other by a single methylene group generally belong to the essential fatty acids which are all either ω3 or ω6 fatty acids, meaning that there will be a double bond at carbon 3 or 6, respectively, from the end of the molecule.

PUFAs are not commonly found in higher plants, which typically produce saturated and mono-unsaturated long chain fatty acids as common constituents of the plant cuticle. They are produced in many algae, mosses and ferns, where they are found in all major glycerol lipids and represent major constituents of membranes [Kaewsuwan06].

Arachidonate (arachidonic acid) is a polyunsaturated ω-6 fatty acid with a 20-carbon chain and four cis-double bonds. It is produced de novo at high levels by mosses, by some lower eukaryotes (e.g. Euglena), and by some marine bacteria adapted to low temperatures and high pressures.

About this Pathway

Some fungi, such as the filamentous fungus Mortierella alpina, are capable of producing a large amount of arachidonate de novo [Yamada87b]. Arachidonate production by certain species of moss is also well documented .

The biosynthesis of arachidonate and icosapentaenoate in the moss Physcomitrella patens starts with linoleate (18:2Δ9,12) and α-linolenate(18:3Δ9,12,15), respectively, and involves sequential Δ6 desaturation, elongation, and Δ5 desaturation. The desaturases and elongases involved in long chain polyunsaturated fatty acids biosynthesis require that the substrates are esterified to coenzyme A [Domergue03]. Fatty acid elongase complexes comprise of the β-keto-acyl-CoA synthase, ketoacyl-CoA reductase, hydroxyacyl-CoA reductase and the enoyl-CoA reductase enzyme activities [Meyer04a].

An acyl-lipid 6-desaturase was identified and cloned in Physcomitrella patens [Girke98], as were a Δ6-acyl-CoA elongase [Zank02] and an acyl-lipid 5-desaturase [Kaewsuwan06]. The Δ5 and Δ6 desaturases are front-loading desatrurases, and introduce the new double bonds between the carboxyl end of the fatty acid and an existing double bond. Unlike mamalian Δ5 and Δ6 desaturases, which act on acyl-coAs, the enzymes from lower plants, fungi, worms and algae prefer to act on fatty acids that are incorporated at the sn-2 position of glycerolipids [Domergue03]. The elongase, on the other hand, acts on coenzyme A-linked substrates. Thus, following the Δ6 desaturation the fatty acids have to be transferred from a lipid to CoA for elongation, after which they are transferred back to a lipid for the Δ5 desaturation [Domergue03].

See also icosapentaenoate biosynthesis I (lower eukaryotes).

Variants: arachidonate biosynthesis II (bacteria), arachidonate biosynthesis III (6-desaturase, mammals), arachidonate biosynthesis IV (8-detaturase, lower eukaryotes), arachidonate biosynthesis V (8-detaturase, mammals)

Created 27-Sep-2006 by Zhang P, TAIR
Revised 25-Oct-2011 by Weerasinghe D, SRI International
Revised 22-Nov-2011 by Caspi R, SRI International
Revised 23-Jan-2012 by Weerasinghe D, SRI International
Revised 22-May-2012 by Weerasinghe D, SRI International


Domergue03: Domergue F, Abbadi A, Ott C, Zank TK, Zahringer U, Heinz E (2003). "Acyl carriers used as substrates by the desaturases and elongases involved in very long-chain polyunsaturated fatty acids biosynthesis reconstituted in yeast." J Biol Chem 278(37);35115-26. PMID: 12835316

Girke98: Girke T, Schmidt H, Zahringer U, Reski R, Heinz E (1998). "Identification of a novel delta 6-acyl-group desaturase by targeted gene disruption in Physcomitrella patens." Plant J 15(1);39-48. PMID: 9744093

Kaewsuwan06: Kaewsuwan S, Cahoon EB, Perroud PF, Wiwat C, Panvisavas N, Quatrano RS, Cove DJ, Bunyapraphatsara N (2006). "Identification and functional characterization of the moss Physcomitrella patens delta5-desaturase gene involved in arachidonic and eicosapentaenoic acid biosynthesis." J Biol Chem 281(31);21988-97. PMID: 16728405

Meyer04a: Meyer A, Kirsch H, Domergue F, Abbadi A, Sperling P, Bauer J, Cirpus P, Zank TK, Moreau H, Roscoe TJ, Zahringer U, Heinz E (2004). "Novel fatty acid elongases and their use for the reconstitution of docosahexaenoic acid biosynthesis." J Lipid Res 45(10);1899-909. PMID: 15292371

Yamada87b: Yamada H, Shimizu S, Shinmen Y (1987). "Production of Arachidonic Acid by Mortierella elongata 1S-5." Agricultural and Biological Chemistry 51(3):785-790.

Zank02: Zank TK, Zahringer U, Beckmann C, Pohnert G, Boland W, Holtorf H, Reski R, Lerchl J, Heinz E (2002). "Cloning and functional characterisation of an enzyme involved in the elongation of Delta6-polyunsaturated fatty acids from the moss Physcomitrella patens." Plant J 31(3);255-68. PMID: 12164806

Other References Related to Enzymes, Genes, Subpathways, and Substrates of this Pathway

Chu80: Chu FLE, Dupuy JL (1980). "The fatty acid composition of three unicellular algal species used as food sources for larvae of the American oyster (Crassostrea virginica)." Lipids 15(5);356-364.

Horrobin92: Horrobin DF (1992). "Nutritional and medical importance of gamma-linolenic acid." Prog Lipid Res 31(2);163-94. PMID: 1334266

Huang99b: Huang YS, Chaudhary S, Thurmond JM, Bobik EG, Yuan L, Chan GM, Kirchner SJ, Mukerji P, Knutzon DS (1999). "Cloning of delta12- and delta6-desaturases from Mortierella alpina and recombinant production of gamma-linolenic acid in Saccharomyces cerevisiae." Lipids 34(7);649-59. PMID: 10478922

Hulanicka64: Hulanicka D, Erwin J, Bloch K (1964). "Lipid metabolism of Euglena gracilis." J Biol Chem 239;2778-87. PMID: 14216427

Johnson97a: Johnson MM, Swan DD, Surette ME, Stegner J, Chilton T, Fonteh AN, Chilton FH (1997). "Dietary supplementation with gamma-linolenic acid alters fatty acid content and eicosanoid production in healthy humans." J Nutr 127(8);1435-44. PMID: 9237935

Lager13: Lager I, Yilmaz JL, Zhou XR, Jasieniecka K, Kazachkov M, Wang P, Zou J, Weselake R, Smith MA, Bayon S, Dyer JM, Shockey JM, Heinz E, Green A, Banas A, Stymne S (2013). "Plant acyl-CoA:lysophosphatidylcholine acyltransferases (LPCATs) have different specificities in their forward and reverse reactions." J Biol Chem 288(52);36902-14. PMID: 24189065

Latendresse13: Latendresse M. (2013). "Computing Gibbs Free Energy of Compounds and Reactions in MetaCyc."

Lederer94: Lederer F (1994). "The cytochrome b5-fold: an adaptable module." Biochimie 76(7);674-92. PMID: 7893819

Leonard00: Leonard AE, Bobik EG, Dorado J, Kroeger PE, Chuang LT, Thurmond JM, Parker-Barnes JM, Das T, Huang YS, Mukerji P (2000). "Cloning of a human cDNA encoding a novel enzyme involved in the elongation of long-chain polyunsaturated fatty acids." Biochem J 350 Pt 3;765-70. PMID: 10970790

Liu01a: Liu L, Li MC, Hu GW, Ge J, Zhang L, Cheng ZH, Xing LJ (2001). "[Expression of delta 6-fatty acid desaturase gene from Mortierella alpina in Saccharomyces cerevisiae]." Sheng Wu Gong Cheng Xue Bao 17(2);161-4. PMID: 11411223

Michaelson98: Michaelson LV, Lazarus CM, Griffiths G, Napier JA, Stobart AK (1998). "Isolation of a Delta5-fatty acid desaturase gene from Mortierella alpina." J Biol Chem 273(30);19055-9. PMID: 9668087

Napier03: Napier JA, Michaelson LV, Sayanova O (2003). "The role of cytochrome b5 fusion desaturases in the synthesis of polyunsaturated fatty acids." Prostaglandins Leukot Essent Fatty Acids 68(2);135-43. PMID: 12538077

ParkerBarnes00: Parker-Barnes JM, Das T, Bobik E, Leonard AE, Thurmond JM, Chaung LT, Huang YS, Mukerji P (2000). "Identification and characterization of an enzyme involved in the elongation of n-6 and n-3 polyunsaturated fatty acids." Proc Natl Acad Sci U S A 97(15);8284-9. PMID: 10899997

Rubio06: Rubio S, Larson TR, Gonzalez-Guzman M, Alejandro S, Graham IA, Serrano R, Rodriguez PL (2006). "An Arabidopsis mutant impaired in coenzyme A biosynthesis is sugar dependent for seedling establishment." Plant Physiol 140(3);830-43. PMID: 16415216

Sakuradani99a: Sakuradani E, Kobayashi M, Shimizu S (1999). "Delta6-fatty acid desaturase from an arachidonic acid-producing Mortierella fungus. Gene cloning and its heterologous expression in a fungus, Aspergillus." Gene 238(2);445-53. PMID: 10570972

Sayanova97: Sayanova O, Smith MA, Lapinskas P, Stobart AK, Dobson G, Christie WW, Shewry PR, Napier JA (1997). "Expression of a borage desaturase cDNA containing an N-terminal cytochrome b5 domain results in the accumulation of high levels of delta6-desaturated fatty acids in transgenic tobacco." Proc Natl Acad Sci U S A 94(8);4211-6. PMID: 9108131

Shimizu88: Shimizu S, Shinmen Y, Kawashima H, Akimoto K, Yamada H (1988). "Fungal mycelia as a novel source of eicosapentaenoic acid. Activation of enzyme(s) involved in eicosapentaenoic acid production at low temperature." Biochem Biophys Res Commun 150(1);335-41. PMID: 2827674

Sperling00: Sperling P, Lee M, Girke T, Zahringer U, Stymne S, Heinz E (2000). "A bifunctional delta-fatty acyl acetylenase/desaturase from the moss Ceratodon purpureus. A new member of the cytochrome b5 superfamily." Eur J Biochem 267(12);3801-11. PMID: 10848999

Stymne84: Stymne S, Stobart AK (1984). "Evidence for the reversibility of the acyl-CoA:lysophosphatidylcholine acyltransferase in microsomal preparations from developing safflower (Carthamus tinctorius L.) cotyledons and rat liver." Biochem J 223(2);305-14. PMID: 6497849

Zhou07: Zhou XR, Robert SS, Petrie JR, Frampton DM, Mansour MP, Blackburn SI, Nichols PD, Green AG, Singh SP (2007). "Isolation and characterization of genes from the marine microalga Pavlova salina encoding three front-end desaturases involved in docosahexaenoic acid biosynthesis." Phytochemistry 68(6);785-96. PMID: 17291553

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 Pathway Tools version 19.5 (software by SRI International) on Sat Apr 30, 2016, biocyc11.