Multiple Functions as Lipase, Steryl Ester Hydrolase, Phospholipase, and Acyltransferase of Tgl4p from the Yeast Saccharomyces cerevisiae

Abstract

Triacylglycerol (TAG) hydrolysis, membrane lipid biosynthesis, and lipid turnover are largely interlinked processes. In yeast, TAG is mobilized by three TAG lipases named Tgl3p, Tgl4p, and Tgl5p, which are localized to lipid particles/droplets. These TAG lipases posses a conserved GXSXG motif that is characteristic of hydrolytic enzymes. Here, we demonstrated that the yeast TAG lipase Tgl4p, the functional ortholog of the adipose TAG lipase, ATGL, catalyzes multiple functions in lipid metabolism. An extended domain and motif search analysis revealed that Tgl4p bears not only a lipase consensus domain but also a conserved motif for calcium-independent phospholipase A 2 . We show that Tgl4p exhibits TAG lipase, steryl ester hydrolase, and phospholipase A 2 activities, but surprisingly it also catalyzed the acyl-CoA-dependent acylation of lysophosphatidic acid to phosphatidic acid (PA). Heterologous overexpression of Tgl4p in Pichia pastoris increased total phospholipid and specifically PA synthesis. Moreover, deletion of TGL4 in Saccharomyces cerevisiae showed an altered pattern of phosphatidylcholine and PA molecular species. Altogether, our data suggest that yeast Tgl4p functions as a hydrolytic enzyme in lipid degradation but also contributes to fatty acid channeling and phospholipid remodeling.

Regulation of the Yeast Triacylglycerol Lipase Tgl3p by Formation of Nonpolar Lipids

“…The three yeast TG lipases identified so far, Tgl3p, Tgl4p, and Tgl5p, catalyze hydrolysis of TG to diacylglycerols (DG) and free fatty acids. Interestingly, previous studies from our labora-tory described additional functions of these enzymes as lysophospholipid acyltransferases with preferences for either lysophosphatidylethanolamine or lysophosphatidic acid, respectively, as substrates (23)(24)(25). In tgl3⌬ and tgl5⌬ strains, the amounts of total phospholipids are reduced supporting the view that acyltransferase activities of Tgl3p and Tgl5p are also relevant in vivo.…”

Morphogenesis checkpoint kinase Swe1 is the executor of lipolysis-dependent cell-cycle progression

“…Absence of lipolysis in mutants lacking TGL3 and TGL4 results in up to threefold elevated levels of TG and reduced levels of phosphatidylcholine and sphingolipids (4,12,16,17), indicating that TG breakdown provides precursors for these lipids or generates some regulatory factors required for their synthesis. The rate of phosphatidylinositol (PI) synthesis after readdition of inositol to inositol-starved cells is reduced by 50% in lipase-deficient cells; the boost of PI synthesis under inositol refeeding conditions is completely abolished if de novo FA synthesis is additionally blocked in the lipase mutants by the inhibitor cerulenin (18).…”

“…Degradation of TG in yeast is governed by the major lipid droplet (LD)-associated lipases, encoded by TGL3 and TGL4 (4, 12); both enzymes belong to the patatin-domaincontaining family of proteins, members of which play a crucial role in lipid homeostasis also in mammals (13). Multiple additional lipases exist in yeast, but their specific function and contribution to TG homeostasis may be restricted to specific growth conditions (7,14,15).Absence of lipolysis in mutants lacking TGL3 and TGL4 results in up to threefold elevated levels of TG and reduced levels of phosphatidylcholine and sphingolipids (4,12,16,17), indicating that TG breakdown provides precursors for these lipids or generates some regulatory factors required for their synthesis. The rate of phosphatidylinositol (PI) synthesis after readdition of inositol to inositol-starved cells is reduced by 50% in lipase-deficient cells; the boost of PI synthesis under inositol refeeding conditions is completely abolished if de novo FA synthesis is additionally blocked in the lipase mutants by the inhibitor cerulenin (18).…”

Genome mining of fungal lipid-degrading enzymes for industrial applications

“…The steryl ester hydrolase enzymes having an abhydro_lipase domain are involved in steryl ester degradation (Köffel et al, 2005;Müllner et al, 2005;Köffel & Schneiter, 2006), whereas the patatin-domain-containing lipases (triacylglycerol lipases) play essential roles in breakdown of triglyceride (Kienesberger et al, 2009;Rajakumari & Daum, 2010;Yazawa et al, 2012). As a result, these two major groups of lipases seem to be ubiquitous enzymes, which might be essential for yeast and fungal cells to either utilize or mobilize neutral lipids.…”