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: triacylglyceride degradation, triacylglycerol hydrolysis, lipolysis
|Superclasses:||Degradation/Utilization/Assimilation → Fatty Acid and Lipids Degradation|
Triacylglycerol (TAG) degradation is critical to many plants for which lipids rather than carbohydrates are the major seed storage reserves. The breakdown of the seed storage lipid provides carbon skeletons and energy that can drive postgerminative plant growth before the plant root system and photosynthetic capacity are fully established.
TAG degradation occurs in the seed oil body where TAG is deposited and stored. The liberated free fatty acids are transported to glyoxysomes where they are converted to acetyl-CoAs via the beta oxidation pathway (fatty acid β-oxidation II (peroxisome)). The acetyl-CoAs are eventually converted to carbohydrates via glyoxylate cycle (superpathway of glyoxylate cycle and fatty acid degradation). It is generally thought that the hydrolytic attack of TAG primarily occurs at the sn-1 or sn-3 positions but not the sn-2 position. Sn-2 monoacylglycerols are naturally racemized to sn-1 monoacylglycerols to be completely hydrolyzed by monoacylglycerol lipases (pg255 in [Dey97]).
Despite the importance of the pathway for plants, there is still not much known about the plant enzymes and genes of the pathway, especially di- and mono-acylglycerol lipases. To date, only an Arabidopsis triacylglycerol lipase has been biochemically and genetically proven to play a role in the breakdown of seed storage TAG during seed germination.
In Saccharomyces cerevisiae the degradation of TAG and phospholipids is taking place in the lipid droplets [Czabany07, Henry12] where all the tri- to monoacylglycerol lipases of yeast have been shown to be located and enzymatically active [Athenstaedt99, Athenstaedt05]. The major TAG lipase TGL3p also exhibited DAG lipase activity in vitro [Kurat06]. The other TAG lipase of importance in yeast, i.e. TGL4 has even been demonstrated to represent a multi-functional enzyme which also acts as steryl ester hydrolase, sn-1 and sn-2 phospholipase A2 and acyl-CoA dependent lysophospholipid acyltransferase [Rajakumari10a]. In addition, the TAG lipase TGL5 has been found to be bifunctional and furthermore catalyzes the acylation of lysophosphilipids [Rajakumari10] indicating that TAG lipase enzymes of yeast are likewise involved in catabolic and anabolic pathways of fatty acid metabolism. The in vivo and in vitro activity of the only monoacylglycerol lipase (MGL) in yeast encoded by YJU3 has been demonstrated in Δyju3 mutants which showed no MGL activity but could be rescued by murine monoacylglycerol lipase (mMGL). Moreover, heterologous expressed and purified YJU3 enzyme efficiently hydrolyzed both 1-oleoylglycerol and 2-oleoylglycerol to yield glycerol and oleate [Heier10].
Unification Links: AraCyc:LIPAS-PWY
Athenstaedt05: Athenstaedt K, Daum G (2005). "Tgl4p and Tgl5p, two triacylglycerol lipases of the yeast Saccharomyces cerevisiae are localized to lipid particles." J Biol Chem 280(45);37301-9. PMID: 16135509
Athenstaedt99: Athenstaedt K, Zweytick D, Jandrositz A, Kohlwein SD, Daum G (1999). "Identification and characterization of major lipid particle proteins of the yeast Saccharomyces cerevisiae." J Bacteriol 181(20);6441-8. PMID: 10515935
Eastmond06: Eastmond PJ (2006). "SUGAR-DEPENDENT1 encodes a patatin domain triacylglycerol lipase that initiates storage oil breakdown in germinating Arabidopsis seeds." Plant Cell 18(3);665-75. PMID: 16473965
Heier10: Heier C, Taschler U, Rengachari S, Oberer M, Wolinski H, Natter K, Kohlwein SD, Leber R, Zimmermann R (2010). "Identification of Yju3p as functional orthologue of mammalian monoglyceride lipase in the yeast Saccharomycescerevisiae." Biochim Biophys Acta 1801(9);1063-71. PMID: 20554061
Kurat06: Kurat CF, Natter K, Petschnigg J, Wolinski H, Scheuringer K, Scholz H, Zimmermann R, Leber R, Zechner R, Kohlwein SD (2006). "Obese yeast: triglyceride lipolysis is functionally conserved from mammals to yeast." J Biol Chem 281(1);491-500. PMID: 16267052
Rajakumari10a: Rajakumari S, Daum G (2010). "Multiple functions as lipase, steryl ester hydrolase, phospholipase, and acyltransferase of Tgl4p from the yeast Saccharomyces cerevisiae." J Biol Chem 285(21);15769-76. PMID: 20332534
Holst96: Holst LS, Langin D, Mulder H, Laurell H, Grober J, Bergh A, Mohrenweiser HW, Edgren G, Holm C (1996). "Molecular cloning, genomic organization, and expression of a testicular isoform of hormone-sensitive lipase." Genomics 35(3);441-7. PMID: 8812477
Jandrositz05: Jandrositz A, Petschnigg J, Zimmermann R, Natter K, Scholze H, Hermetter A, Kohlwein SD, Leber R (2005). "The lipid droplet enzyme Tgl1p hydrolyzes both steryl esters and triglycerides in the yeast, Saccharomyces cerevisiae." Biochim Biophys Acta 1735(1);50-8. PMID: 15922657
Kim11: 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
Koffel05: Koffel R, Tiwari R, Falquet L, Schneiter R (2005). "The Saccharomyces cerevisiae YLL012/YEH1, YLR020/YEH2, and TGL1 genes encode a novel family of membrane-anchored lipases that are required for steryl ester hydrolysis." Mol Cell Biol 25(5);1655-68. PMID: 15713625
Kurat09: Kurat CF, Wolinski H, Petschnigg J, Kaluarachchi S, Andrews B, Natter K, Kohlwein SD (2009). "Cdk1/Cdc28-dependent activation of the major triacylglycerol lipase Tgl4 in yeast links lipolysis to cell-cycle progression." Mol Cell 33(1);53-63. PMID: 19150427
Osterlund96: Osterlund T, Danielsson B, Degerman E, Contreras JA, Edgren G, Davis RC, Schotz MC, Holm C (1996). "Domain-structure analysis of recombinant rat hormone-sensitive lipase." Biochem J 319 ( Pt 2);411-20. PMID: 8912675
Schmidt13: Schmidt C, Athenstaedt K, Koch B, Ploier B, Daum G (2013). "Regulation of the yeast triacylglycerol lipase TGl3p by formation of nonpolar lipids." J Biol Chem 288(27);19939-48. PMID: 23673660
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