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Synthesis and turnover of non-polarlipids in yeast

turnover of non-polar lipids in yeast.

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Synthesis and turnover of non-polar lipids in yeast.

While it is a well known fact that lipid turnover is a common process in cells and that it plays a major role in attaining the steady state lipid composition of the cell, the results obtained upon deletion of the acyl-CoA synthetases highlight the actual magnitude of the phenomena: by late stationary phase the cells have turned over an amount of FA corresponding to four times their total content of esterified FA. Given that in WT cells these FA are activated and can reenter lipid metabolism, it also becomes clear that lipid turnover and FA recycling make a major contribution to the acyl-CoA pool in addition to de novo FA synthesis. It is also remarkable that the size of the FFA pool doubles between the end of exponential growth and the time point selected at late stationary phase, indicating that lipid metabolism remains highly active in non-dividing cells.

Synthesis and turnover of non polar lipids in yeast ..

The phospholipases B of yeast have often been mentioned as potential candidates when the need for deacylation is addressed in the context of PL degradation and remodeling , . However, under our experimental conditions these enzymes played no substantial role in constitutive lipid deacylation. Similarly, Tanaka and coworkers showed that, upon deletion of PLB1, PLB2 and PLB3, the choline auxotrophic pem1Δpem2Δ strain (unable to synthesize PC by methylation of PE) retains its ability to grow in media containing short acyl chain PC (diC8PC) as choline source. While their results seem to exempt Plb1p, Plb2p and Plb3p from involvement in the remodeling of an entirely unnatural exogenously provided PL, our results extend this exemption to Nte1p and, most importantly, refer to the endogenous and naturally produced PL content of the cell. These negative results are not entirely surprising since the fact that these proteins possess lysophospholipase in addition to phospholipase B activity does make them suboptimal candidates for the production of lysolipids that should mediate constitutive PL remodeling. In any case, this does not dispute their involvement in non-constitutive processes like glycerophosphodiester formation and lysolipid degradation , , . Rather than taking part in constitutive remodeling these lipases could mainly degrade excessive phospholipids arising from specific culture conditions, a demonstrated role of phospholipase A enzymes in mammalian cells . In yeast the activity of Nte1p is known to behave in such fashion, resulting in enhanced PC turnover when culture conditions such as inositol supplementation, choline supplementation or elevated temperature lead to an increased rate of PI or PC synthesis , , , . Within our experiments Nte1p, but not the other Plb enzymes, did show a role in PL deacylation upon deletion of DGA1, what, as will be discussed ahead, appears to be a situation of increased PL synthesis.

Glossary | Linus Pauling Institute | Oregon State University

De novo synthesis the formation of an essential molecule from simple precursor molecules

All eukaryotes including the yeast contain a lipid storage compartment which is named lipid particle, lipid droplet or oil body. Lipids accumulating in this subcellular fraction serve as a depot of energy and building blocks for membrane lipid synthesis. In the yeast, the major storage lipids are triacylglycerols (TGs) and steryl esters (SEs). An important step in the life cycle of these non-polar lipids is their mobilization from their site of storage and channeling of their degradation components to the appropriate metabolic pathways. A key step in this mobilization process is hydrolysis of TG and SE which is accomplished by lipases and hydrolases. In this review, we describe our recent knowledge of TG lipases from the yeast based on biochemical, molecular biological and cell biological information. We report about recent findings addressing the versatile role of TG lipases in lipid metabolism, and discuss non-polar lipid homeostasis and its newly discovered links to various cell biological processes in the yeast.

Important dates in the history of lipids ..

The role of phospholipids in cell function - ScienceDirect

THE ROLE OF PHOSPHOLIPIDS IN CELL FUNCTION William Dowhan lo II
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