Due to its genetic tractability and increasing wealth of accessible data, the yeast Saccharomyces cerevisiae is a model system of choice for the study of the genetics, biochemistry, and cell biology of eukaryotic lipid metabolism. Glycerolipids (e.g., phospholipids and triacylglycerol) and their precursors are synthesized and metabolized by enzymes associated with the cytosol and membranous organelles, including endoplasmic reticulum, mitochondria, and lipid droplets. Genetic and biochemical analyses have revealed that glycerolipids play important roles in cell signaling, membrane trafficking, and anchoring of membrane proteins in addition to membrane structure. The expression of glycerolipid enzymes is controlled by a variety of conditions including growth stage and nutrient availability. Much of this regulation occurs at the transcriptional level and involves the Ino2–Ino4 activation complex and the Opi1 repressor, which interacts with Ino2 to attenuate transcriptional activation of UASINO-containing glycerolipid biosynthetic genes. Cellular levels of phosphatidic acid, precursor to all membrane phospholipids and the storage lipid triacylglycerol, regulates transcription of UASINO-containing genes by tethering Opi1 to the nuclear/endoplasmic reticulum membrane and controlling its translocation into the nucleus, a mechanism largely controlled by inositol availability. The transcriptional activator Zap1 controls the expression of some phospholipid synthesis genes in response to zinc availability. Regulatory mechanisms also include control of catalytic activity of glycerolipid enzymes by water-soluble precursors, products and lipids, and covalent modification of phosphorylation, while in vivo function of some enzymes is governed by their subcellular location. Genome-wide genetic analysis indicates coordinate regulation between glycerolipid metabolism and a broad spectrum of metabolic pathways.

https://www.genetics.org/content/genetics/190/2/317.full.pdf

Metabolism and Regulation of Glycerolipids in the Yeast Saccharomyces cerevisiae

Methods for lipase detection and assay: a critical review

http://www.jbc.org/content/281/1/491.full.pdf

Obese Yeast: Triglyceride Lipolysis Is Functionally Conserved from Mammals to Yeast

Triacylglycerols (TAGs), steryl esters (SEs) and wax esters (WEs) form the group of neutral lipids. Whereas TAGs are present in all types of cell, the occurrence of SEs in prokaryotes is questionable, and the presence of WEs as storage molecules is restricted to plants and a few bacteria. Here, we summarize recent knowledge on the formation, storage and degradation of TAGs and SEs in various cell types. We describe the biochemical pathways involved in TAG and SE synthesis and discuss the subcellular compartmentation of these processes. Recently, several novel enzymes governing the metabolism of storage lipids have been identified and characterized. Regulatory aspects of neutral lipid storage are just beginning to be understood. Finally, we describe consequences of defects in neutral lipid metabolism. Since severe diseases like atherosclerosis, obesity and type 2 diabetes are caused by lipid accumulation, mechanisms underlying neutral lipid synthesis, depot formation and mobilization are of major interest for curing such diseases that are increasingly associated with modern civilization.

The life cycle of neutral lipids: synthesis, storage and degradation.

Methods for detection and characterization of lipases: A comprehensive review

The lipid droplet enzyme Tgl1p hydrolyzes both steryl esters and triglycerides in the yeast, Saccharomyces cerevisiae

We developed a specific method for determination and discrimination of lipo-/estero-lytic enzymes in crude lipase preparations Here we study the composition of commercial porcine pancreatic lipase (PPL), since it is widely used for bioconversions of synthetic and natural substrates Our method is based on incubation of enzyme samples with fluorescently labeled alkyl- or dialkylglyceryl-phosphonates in an appropriate solvent followed by protein separation by electrophoresis and fluorescence detection with a CCD camera After incubation with short-chain alkylphosphonate solubilized by taurodeoxycholate, crude PPL preparations showed a very weak band at 50 kDa, which is indicative of low PPL concentrations in these samples In addition, seven other fluorescent bands were detected The band at the lowest molecular weight corresponded to alpha-chymotrypsin Two intensive fluorescent bands were in the molecular weight range of chymotrypsinogen (26 kDa) and four weak bands were in the range 20-24 kDa Long-chain dialkylglycerophosphonate labeled two protein bands in crude PPL: alpha-chymotrypsin and a very intensive band corresponding to the molecular weight of chymotrypsinogen Detection of cholesterol esterase (98 kDa) in crude PPL preparations depended on addition of the protease inhibitor phenylmethylsulfonyl fluoride (PMSF) to the incubation mix, as demonstrated by spiking with cholesterol esterase Thus, commercial crude PPL preparations contain a variety of estero-/lipo-lytic enzymes in addition to rather low amounts of active PPL, which should be considered when using crude PPL for bioconversions Our method can also be used to show whether an isolated esterolytic activity corresponds to a single protein or isoenzymes Here we confirm by 2D-electrophoretic separation of "pure" PPL that PPL exists as isoenzymes in different glycosylated forms

Hubert Scholze

Papers

The lipid droplet enzyme Tgl1p hydrolyzes both steryl esters and triglycerides in the yeast, Saccharomyces cerevisiae

Identification of various lipolytic enzymes in crude porcine pancreatic lipase preparations using covalent fluorescent inhibitors.

Fluorescent Inhibitors for the Qualitative and Quantitative Analysis of Lipolytic Enzymes

Fluorescent Probes for Lipolytic Enzymes