title: Defects in triacylglycerol lipolysis affect synthesis of triacylglycerols and steryl esters in the yeast.
abstract: Tgl3p, Tgl4p and Tgl5p are the major triacylglycerol lipases of the yeast Saccharomyces cerevisiae catalyzing degradation of triacylglycerols stored in lipid droplets. Previous results from our laboratory (Athenstaedt and Daum, 2005, J. Biol. Chem. 280, 37301-37309) demonstrated that a yeast strain lacking all three triacylglycerol lipases accumulates not only triacylglycerols at high amount, but also steryl esters. Here we show a metabolic link between synthesis and mobilization of non-polar lipids. In particular, we demonstrate that a block in tri-acylglycerol degradation in a tgl3∆tgl4∆tgl5∆ triple mutant lacking all major triacylglycerol lipases causes marked changes in non-polar lipid synthesis. Under these conditions formation of triacylglycerols is reduced, whereas steryl ester synthesis is enhanced as shown by quantification of non-polar lipids, in vivo labeling of lipids using [(14)C]oleic acid and [(14)C]acetic acid as precursors, and enzyme analyses in vitro. In summary, this study demonstrates that triacylglycerol metabolism and steryl ester metabolism are linked processes. The importance of balanced storage and degradation of these components for lipid homeostasis in the yeast is highlighted.
authors.affiliation: Institute of Biochemistry, Graz University of Technology, NaWi Graz, Austria.
authors.forename: Claudia
authors.initials: C
authors.lastname: Schmidt
authors.affiliation: Institute of Biochemistry, Graz University of Technology, NaWi Graz, Austria; Institute of Molecular Biosciences, University of Graz, NaWi Graz, Austria.
authors.forename: Karin
authors.initials: K
authors.lastname: Athenstaedt
authors.affiliation: Institute of Biochemistry, Graz University of Technology, NaWi Graz, Austria.
authors.forename: Barbara
authors.initials: B
authors.lastname: Koch
authors.affiliation: Institute of Biochemistry, Graz University of Technology, NaWi Graz, Austria.
authors.forename: Birgit
authors.initials: B
authors.lastname: Ploier
authors.affiliation: Institute of Biochemistry, Graz University of Technology, NaWi Graz, Austria.
authors.forename: Martina
authors.initials: M
authors.lastname: Korber
authors.affiliation: Institute of Plant Sciences, University of Graz, NaWi Graz, Austria.
authors.forename: Günther
authors.initials: G
authors.lastname: Zellnig
authors.affiliation: Institute of Biochemistry, Graz University of Technology, NaWi Graz, Austria. Electronic address: guenther.daum@tugraz.at.
authors.forename: Günther
authors.initials: G
authors.lastname: Daum
keywords: Lipase; Lipid droplet; Steryl ester; Triacylglycerol; Yeast