Note: a dashed line (without arrowheads) between two compound names is meant to imply that the two names are just different instantiations of the same compound -- i.e. one may be a specific name and the other a general name, or they may both represent the same compound in different stages of a polymerization-type pathway. 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.
|Superclasses:||Biosynthesis → Fatty Acids and Lipids Biosynthesis|
Some taxa known to possess this pathway include : Carthamus tinctorius
Expected Taxonomic Range: Spermatophyta
Triacyglycerols (TAG) from vegetable oils are a major source of essential fatty acids in human diet, namely polyunsaturated fatty acids (PUFA) linoleate (18:2) and linolenate (18:3). In oilseeds, TAG is synthesized via the Kennedy pathway, where the precursor diacylglycerol (DAG) is de novo synthesized from glycerol-3-phosphate. In addition to the Kennedy pathway, there are several other paths supplying DAG for TAG biosynthesis during seed development in plants [Bates09]. They involve a reverse activity of CDP-choline:1,2-diacylglycerol cholinephosphotransferas, and/or a novel enzyme phosphatidylcholine:diacylglycerol cholinephosphotransferase. Since further desaturation of 18:1 to form 18:2 and 18:3 occurs mainly in phosphatidylcholine (PC), these alternative paths can provide PC-derived DAG species which are enriched in PUFA for TAG synthesis. Further more, an acyl editing (acyl exchange) mechanism also exists that can further enrich PUFA in oilseed TAG [Bates09].
Acyl exchange between acyl-CoA and PC has been detected in a number of plant species including microsomal preparations of developing safflower cotyledons [Stymne84] and developing soybean embryos [Bates09]. Further experiments are required to reveal whether a reverse activity of acyl-CoA:lysophosphatidylcholine acyltransferase (LPCAT, 18.104.22.168) or a phospholipase A (22.214.171.124, 126.96.36.199), or both are involved in acyl-CoA and lysophosphatidylcholine generation [Bates09]. In either case, PC-derived acyl-CoAs, which are rich in PUFA, can feed into the Kennedy pathway for TAG synthesis. Lysophosphatidylcholines can be converted back to PC to replenish the PC pool by the forward reaction of 188.8.131.52. In addition, in the forward reaction de novo synthesized acyl-CoAs can be incorporated into PC.
Bates09: Bates PD, Durrett TP, Ohlrogge JB, Pollard M (2009). "Analysis of acyl fluxes through multiple pathways of triacylglycerol synthesis in developing soybean embryos." Plant Physiol 150(1);55-72. PMID: 19329563
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
Dennis91: Dennis MW, Kolattukudy PE (1991). "Alkane biosynthesis by decarbonylation of aldehyde catalyzed by a microsomal preparation from Botryococcus braunii." Arch Biochem Biophys 287(2);268-75. PMID: 1898004
Fulda02: Fulda M, Shockey J, Werber M, Wolter FP, Heinz E (2002). "Two long-chain acyl-CoA synthetases from Arabidopsis thaliana involved in peroxisomal fatty acid beta-oxidation." Plant J 32(1);93-103. PMID: 12366803
Holk02: Holk A, Rietz S, Zahn M, Quader H, Scherer GF (2002). "Molecular identification of cytosolic, patatin-related phospholipases A from Arabidopsis with potential functions in plant signal transduction." Plant Physiol 130(1);90-101. PMID: 12226489
Ioki12: Ioki M, Baba M, Bidadi H, Suzuki I, Shiraiwa Y, Watanabe MM, Nakajima N (2012). "Modes of hydrocarbon oil biosynthesis revealed by comparative gene expression analysis for race A and race B strains of Botryococcus braunii." Bioresour Technol 109;271-6. PMID: 22257857
Ishiguro01: Ishiguro S, Kawai-Oda A, Ueda J, Nishida I, Okada K (2001). "The DEFECTIVE IN ANTHER DEHISCIENCE gene encodes a novel phospholipase A1 catalyzing the initial step of jasmonic acid biosynthesis, which synchronizes pollen maturation, anther dehiscence, and flower opening in Arabidopsis." Plant Cell 2001;13(10);2191-209. PMID: 11595796
Kim11a: Kim EY, Seo YS, Kim WT (2011). "AtDSEL, an Arabidopsis cytosolic DAD1-like acylhydrolase, is involved in negative regulation of storage oil mobilization during seedling establishment." J Plant Physiol. PMID: 21477884
Lewin01: Lewin TM, Kim JH, Granger DA, Vance JE, Coleman RA (2001). "Acyl-CoA synthetase isoforms 1, 4, and 5 are present in different subcellular membranes in rat liver and can be inhibited independently." J Biol Chem 276(27);24674-9. PMID: 11319232
Malhotra99: Malhotra KT, Malhotra K, Lubin BH, Kuypers FA (1999). "Identification and molecular characterization of acyl-CoA synthetase in human erythrocytes and erythroid precursors." Biochem J 344 Pt 1;135-43. PMID: 10548543
Noiriel04: Noiriel A, Benveniste P, Banas A, Stymne S, Bouvier-Nave P (2004). "Expression in yeast of a novel phospholipase A1 cDNA from Arabidopsis thaliana." Eur J Biochem 271(18);3752-64. PMID: 15355352
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
Ryu05: Ryu SB, Lee HY, Doelling JH, Palta JP (2005). "Characterization of a cDNA encoding Arabidopsis secretory phospholipase A2-alpha, an enzyme that generates bioactive lysophospholipids and free fatty acids." Biochim Biophys Acta 1736(2);144-51. PMID: 16140037
Schnurr02: Schnurr JA, Shockey JM, de Boer GJ, Browse JA (2002). "Fatty acid export from the chloroplast. Molecular characterization of a major plastidial acyl-coenzyme A synthetase from Arabidopsis." Plant Physiol 129(4);1700-9. PMID: 12177483
Shockey02: Shockey JM, Fulda MS, Browse JA (2002). "Arabidopsis contains nine long-chain acyl-coenzyme a synthetase genes that participate in fatty acid and glycerolipid metabolism." Plant Physiol 129(4);1710-22. PMID: 12177484
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