Mutants of Saccharomyces cerevisiae deficient in acyl‐CoA synthetases secrete fatty acids due to interrupted fatty acid recycling

Abstract

In the present study, acyl‐CoA synthetase mutants of Saccharomyces cerevisiae were employed to investigate the impact of this activity on certain pools of fatty acids. We identified a genotype responsible for the secretion of free fatty acids into the culture medium. The combined deletion of Faa1p and Faa4p encoding two out of five acyl‐CoA synthetases was necessary and sufficient to establish mutant cells that secreted fatty acids in a growth‐phase dependent manner. The mutants accomplished fatty acid export during exponential growth‐phase followed by fatty acid re‐import into the cells during the stationary phase. The data presented suggest that the secretion is driven by an active component. The fatty acid re‐import resulted in a severely altered ultrastructure of the mutant cells. Additional strains deficient of any cellular acyl‐CoA synthetase activity revealed an almost identical phenotype, thereby proving transfer of fatty acids across the plasma membrane independent of their activation with CoA. Further experiments identified membrane lipids as the origin of the observed free fatty acids. Therefore, we propose the recycling of endogenous fatty acids generated in the course of lipid remodelling as a major task of both acyl‐CoA synthetases Faa1p and Faa4p.

Ypk1, the yeast orthologue of the human serum- and glucocorticoid-induced kinase, is required for efficient uptake of fatty acids

“…Converting fatty acids to acyl-CoAs and downstream metabolic intermediates increases cellular fatty-acid uptake, possibly by limiting efflux of the free fatty acid and/or by removing the free fatty acid from the equilibrium between extracellular and intracellular free-fatty-acid concentrations (Milger et al, 2006). Consistent with such a view, a yeast faa1⌬ faa4⌬ double mutant has recently been shown to export fatty acids into the culture medium (Michinaka et al, 2003;Scharnewski et al, 2008). This mode of fatty-acid export is not compatible with vectorial acylation, because ATP and CoA required for the synthesis of acyl-CoA would need to be present in the extracellular space (Scharnewski et al, 2008).…”

Combinatorial Engineering of Yarrowia lipolytica as a Promising Cell Biorefinery Platform for the de novo Production of Multi-Purpose Long Chain Dicarboxylic Acids

“…This is because the generation of free fatty acids, particularly unsaturated ones, causes toxicity in the cell with deficient lipid body formation [87]. This occurs for several reasons: the destabilizing effect of fatty acid overproduction on the cellular membrane [80,88], the harmful effects of oxidative species derived from the oxidation of unsaturated fatty acids [89], and a lack of protection against excess lipid intermediates [90].…”

“…Inactivation of FAA1 can interfere with the re-activation of released fatty acids that could serve in energy production, membrane maintenance, or triglyceride (TAG) homeostasis [49,79]. Deletion of the FAA1 and FAA4 genes in S. cerevisiae have been found to interfere with fatty acid incorporation in phospholipids or TAG, while generating a free fatty acid-producing phenotype [80].…”

Advanced biofuel production in microbes

“…Deletion of FAA1 from the wild-type yeast strain led to fatty acid secretion, although it did not account for all the fatty acid secretion observed in the mutant strain. To determine the genotype responsible for fatty acid secretion in S. cerevisiae, Scharnewski et al [49] deleted two of the four acylCoA synthases, FAA1 and FAA4. After these deletions the yeast strain was able to secrete 220 µmol/L of free fatty acids.…”