Staff Members of the Institute of Biochemistry, TU - Institut für ...

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6. Spanova, M. and Daum, G. Squalene – Biochemistry, Molecular Biology, Process Biotechnology and Applications Eur. J. Lipid Sci. Technol. 113 (2011) 1299-1320 7. Athenstaedt, K. and Daum, G. Lipid storage: Yeast we can! Eur. J. Lipid Sci. Technol. 113 (2011) 1188-1197 Awards Karlheinz Grillitsch Award for best poster Characterization of Pichia pastoris plasma membrane Non-conventional yeasts in the Postgenomic Era (NCY-2011), Lviv, Ukraine, 11-14 September 2011 Günther Daum Normann Medal of the German Society of Lipid Research (DGF) Award Lecture: Lipid Storage: Yeast we can! 9 th Euro Fed Lipid Congress, Oils, Fats and Lipids for a Healthy and Sustainable World, Rotterdam, The Netherlands, 18-21 September 2011 Susanne Horvath spent a research semester at the Institute of Biochemistry and Molecular Biology, ZBMZ, University of Freiburg, Germany, in the laboratory of N. Pfanner. This stay abroad was supported by the FWF PhD Program Molecular Enzymology. 24
Molecular Biology Group Group leader: Karin Athenstaedt Two triacylglycerol synthases of the oleaginous yeast Yarrowia lipolytica The oleaginous yeast Yarrowia lipolytica has an outstanding capacity to accumulate huge amounts of triacylglycerols (TAG). Along with other neutral lipids, TAG are stored in lipid particles, cell compartments with a rather simple structure. A neutral lipid core mainly formed of TAG and steryl esters is surrounded by a phospholipid monolayer with few proteins embedded. By growing Yarrowia lipolytica cells in media containing, e.g., industrial fats or glycerol as a carbon source, the amount of TAG can be increased up to 40% of cell dry weight. This ability leads to its application in biotechnological processes such as single cell oil production or production of nutrients enriched in essential fatty acids which can serve as nutritional complements. Despite its industrial application information about TAG (lipid) metabolism in Yarrowia lipolytica is rather limited. Homology searches with TAG synthases of other yeast species as queries highlighted two candidate gene-products of the oleaginous yeast potentially catalyzing the formation of TAG. In the respective single deletion mutants the amount of TAG is significantly decreased. To investigate whether these candidate genes encode true TAG synthases these genes were heterologously expressed in cells of a Saccharomyces cerevisiae mutant defective in neutral lipid synthesis and as a consequence lacking lipid particles. Heterologous expression of both polypeptides restored the formation of lipid particles in host cells. Lipid analyses revealed that the neutral lipid core of lipid particles in the respective host cells was formed of TAG (Fig. 1). A B S STE E S + STE TAG E 1 2 3 4 5 Biosynthesis of phosphatidic acid in yeast Figure 1: Heterologous expression of Yarrowia lipolytica TAG synthases restores the formation of TAG (lanes 4 and 5) in mutant cells of the budding yeast Saccharomyces cerevisiae otherwise lacking neutral lipids (lane 3). Lane 1: standard containing ergosterol (E), triacylglycerols (TAG) and sterol esters (STE); lane 2: neutral lipid pattern of the corresponding Saccharomyces cerevisiae wild-type strain. S: squalene. Phosphatidic acid is of utmost importance, since it is the key intermediate for the formation of all glycerolipids, namely glycerophospholipids (membrane lipids) and triacylglycerols (storage lipids). Furthermore, this lipid functions in cell signaling. In all eukaryotic organisms enzymes catalyzing phosphatidic acid biosynthesis occur in redundancy. One reason for the existence of isoenzymes may be the formation of different phosphatidic acid pools supplying different pathways. In this project this hypothesis is tested in the model organism yeast Saccharomyces cerevisiae, which contains two glycerol-3-phosphate acyltransferases, Gat1p 25
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