Overexpression of genes of the fatty acid biosynthetic pathway leads to accumulation of sterols in Saccharomyces cerevisiae

Abstract

Saccharomyces cerevisiae strains with deregulated sterol and fatty acid biosynthesis pathways were analysed for sterol and fatty acid content and mRNA profiles, with the aim of identifying interactions between lipid biosynthesis pathways. Acetyl CoA carboxylase ACC1 and fatty acid synthases FAS1/FAS2 were overexpressed in wild‐type and squalene‐overproducing strains. ACC1 overexpression led to decreased fatty acid content in the squalene‐overproducing strain (factor of 0.7), while sterols and squalene were increased (factor of 1.5). In the wild‐type strain, ACC1 overexpression led to increased levels of both fatty acids and squalene/sterols (factors of 4.0 and 1.7, respectively). This parallel activation of the two pathways seems to be due to transcriptional co‐regulation of ACC1 and HMG1. While FAS1 and FAS2 overexpression had no effect in the wild‐type strain, FAS2 overexpression induced significant increase of sterols and squalene (factors of 7.2 and 1.3, respectively) and a concomitant decrease of both saturated and unsaturated fatty acids in the squalene‐overproducing strain (factor of 0.6). The microarray expression profiles showed that genes upregulated in ACC1‐overexpressing strains are FAS1, ERG11, ERG28, ERG5, ERG2 and ERG20, supporting the observed increase of zymosterol and saturated fatty acids. The high ACC1 expression level due to overexpression correlated with increased transcript levels of sphingolipid and sterol biosynthesis genes. The relationship between was shown using the Pathway Studio™ program. Copyright © 2012 John Wiley & Sons, Ltd.

Recent advances in biosynthesis of fatty acids derived products in Saccharomyces cerevisiae via enhanced supply of precursor metabolites

“…For example, ACC1 and HMG1 were found to be transcriptionally co-regulated [60], since the overexpression of ACC1 led to increased production of both fatty acids and squalene/sterols. Interestingly, the overexpression of ACC1 in a squalene overproducing strain led to decreased fatty acids production and increased level of squalene/sterols [60]. Since malonyl-CoA biosynthesis and squalene/sterols biosynthesis compete for the same precursor acetyl-CoA, squalene/sterols biosynthetic pathway should be downregulated in the ACC1 overexpression strain to achieve the maximal metabolic fluxes to malonyl-CoA and FAB.…”

“…For example, ACC1 and HMG1 were found to be transcriptionally co-regulated [60], since the overexpression of ACC1 led to increased production of both fatty acids and squalene/sterols. Interestingly, the overexpression of ACC1 in a squalene overproducing strain led to decreased fatty acids production and increased level of squalene/sterols [60].…”

Combinatorial metabolic engineering of Saccharomyces cerevisiae for terminal alkene production

“…The de novo fatty acid biosynthesis in S. cerevisiae requires acetyl-CoA carboxylase (ACC1; encoded by the ACC1) and fatty acid synthase complex (FAS; encoded by FAS1 and FAS2) (Ruenwai et al, 2009;Runguphan and Keasling;Shin et al, 2012;Tai and Stephanopoulos, 2013). ACC1 converts acetyl-CoA into malonyl-CoA, and the overexpression of ACC1 results in increase in final fatty acid level (Ruenwai et al, 2009;Tai and Stephanopoulos, 2013).…”

Fatty Acid Composition in Ergosteryl Esters and Triglycerides from the Fungus Ganoderma lucidum

“…Therefore, a surplus of free sterols in the endoplasmic reticulum is alleviated via esterification with fatty acids by two acyltransferases to maintain intracellular free sterol at nontoxic concentrations [1]. When the biosynthesis of ergosterol increases, the esterification of ergosterols additionally needs an increased quantity of fatty acids for the storage of ergosterols in cells and the biosynthesis of fatty acids increases [19]. Although being unnecessary for fungal viability, steryl esters storage and mobilization contribute markedly to sterol homeostasis and distribution [3].…”