Triacylglycerol biosynthesis (Arabidopsis thaliana)

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1-4PhosphateWateracyltransferaseTAG1L-Phosphatidic acida 1,2-diacylglycerolglycerol-3-phosphate acyltransferaseCoenzyme Asn-glyceryl-3-phosphateLPP3a 2-lysophosphatidatea phosphatidylcholineCoenzyme Aa fatty acyl CoAa fatty acyl CoAa triacylglycerolPDATdiacylglycerol acyltransferaseLPP1PAP2LPP21-acylglycerol-3-phosphate O-acyltransferaseCoenzyme Aa fatty acyl CoA


Triacylglycerol (TAG) is the major lipid reserve in plants and animals. The assembly of TAG occurs in the endoplasmic reticulum (ER). Four consecutive reactions are catalyzed by ER membrane bound enzymes. The two intermediates, phosphatidate and 1,2-diacylglycerol, are also substrates for the synthesis of membrane lipids glycosylglycerides and phosphoglycerides. Thus, the last step in the pathway, catalyzed by diacylglycerol acyltransferase, is the only dedicated step in triacylglycerol synthesis.

The traditional Kennedy pathway does not include the reaction (EC, phospholipid:diacylglycerol acyltransferase, PDAT) where phospholipid is utilized as the acyl donor in TAG formation. The role of the PDAT route in TAG biosynthesis was clearly shown in yeast[ Dahlqvist00 ]. PDAT activity in plants was demonstrated in a few oil seed plants including caster bean[ Dahlqvist00 ]. The caster bean seeds have a high content of ricinoleat in the seed oil. Ricinoleat and other unusual fatty acids are modified from acyl groups linked to phospholipids, and transferred to TAG afterwards. PDAT was proposed playing an important role in the last step. However, the contribution of PDAT to TAG biosynthesis in other plants is not clear. Overexpressing or knockout of the Arabidopsis PDAT had no effect on TAG biosynthesis[ Stahl04 , Mhaske05 ].

The constitution of different species of saturated and unsaturated fatty acids at the sn-1, sn-2, and sn-3 positions of the glycerol backbone varies among different plants, and is determined by substrate specificities of the three acyltransferases involved in this pathway. The composition of distinct fatty acids in TAG determines the quality and property of lipids of different plants, and also contributes to cold temperature sensitivity of different plants.

The pathway and description were copied from Gramene and AraCyc:

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  1. Mhaske V, Beldjilali K, Ohlrogge J, Pollard M; ''Isolation and characterization of an Arabidopsis thaliana knockout line for phospholipid: diacylglycerol transacylase gene (At5g13640).''; Plant Physiol Biochem, 2005 PubMed Europe PMC Scholia
  2. Dahlqvist A, Stahl U, Lenman M, Banas A, Lee M, Sandager L, Ronne H, Stymne S; ''Phospholipid:diacylglycerol acyltransferase: an enzyme that catalyzes the acyl-CoA-independent formation of triacylglycerol in yeast and plants.''; Proc Natl Acad Sci U S A, 2000 PubMed Europe PMC Scholia
  3. St��Ωhl U, Carlsson AS, Lenman M, Dahlqvist A, Huang B, Banas W, Banas A, Stymne S; ''Cloning and functional characterization of a phospholipid:diacylglycerol acyltransferase from Arabidopsis.''; Plant Physiol, 2004 PubMed Europe PMC Scholia
  4. Zou J, Wei Y, Jako C, Kumar A, Selvaraj G, Taylor DC; ''The Arabidopsis thaliana TAG1 mutant has a mutation in a diacylglycerol acyltransferase gene.''; Plant J, 1999 PubMed Europe PMC Scholia


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117255view10:01, 19 May 2021EweitzModified title
72458view20:17, 16 November 2013AlexanderPicoRemoved unsupported (likely accidental) xml in comment field
72381view13:55, 13 November 2013EgonwAdded a bunch of missing metabolite identifiers.
71853view20:14, 18 October 2013MaintBotUpdated data sources
70200view04:48, 13 July 2013MaintBotupdated to 2013 schema
67720view11:54, 26 June 2013DdiglesOntology Term : 'triacylglycerol biosynthetic pathway' added !
40488view19:13, 1 March 2011MaintBotRemoved redundant pathway information and comments
33392view14:45, 30 November 2009MaintBotRemoved group label
28552view18:20, 11 February 2009PjaiswalRemoved prefix 'At' from geneproduct name.
28209view15:01, 6 February 2009ThomasNew pathway

External references


View all...
NameTypeDatabase referenceComment
1-acylglycerol-3-phosphate O-acyltransferaseGeneProductAT3G11430 (TAIR)
Coenzyme AMetabolite85-61-0 (CAS)
L-Phosphatidic acidMetaboliteC00416 (KEGG Compound)
LPP1GeneProductAT2G01180 (TAIR)
LPP2GeneProductAT1G15080 (TAIR)
LPP3GeneProductAT3G02600 (TAIR)
PAP2GeneProductAT3G18220 (TAIR)
PDATGeneProductAT5G13640 (TAIR)
PhosphateMetabolite14265-44-2 (CAS)
TAG1GeneProductAT2G19450 (TAIR)
WaterMetaboliteC00001 (KEGG Compound)
a 1,2-diacylglycerolMetabolite
a 2-lysophosphatidateMetaboliteSynonyms: a 1-acyl-sn-glycerol-3-phosphate , an acyl-sn-glycerol-3P , an acyl-sn-glycerol-3-phosphate , a 1-acyl-sn-glycerol-3P
a fatty acyl CoAMetaboliteCHEBI:37554 (ChEBI)
a phosphatidylcholineMetaboliteC00157 (KEGG Compound)
a triacylglycerolMetaboliteCHEBI:17855 (ChEBI)
acyltransferaseGeneProductAT4G00400 (TAIR)
diacylglycerol acyltransferaseGeneProductAT3G51520 (TAIR)
glycerol-3-phosphate acyltransferaseGeneProductAT1G32200 (TAIR)
sn-glyceryl-3-phosphateMetaboliteC00093 (KEGG Compound)

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