Transport of carboxylic acids in yeasts

Casal, Margarida; Paiva, Sandra; Queirós, Odília; Soares-Silva, Isabel

doi:10.1111/j.1574-6976.2008.00128.x

Cited by 160 publications

(137 citation statements)

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“…Intracellular concentrations were higher when mycelia were maintained at a lower pH (4.0) than at a higher pH (6.5), as would be expected since the higher concentration of undissociated acid in the culture supernatant would have resulted in more galactaric acid diffusing back into the cell and higher overall export costs (5). The cessation of galactarate production after approximately 48 h at pH 4.0 may reflect inhibition of the D-galacturonate dehydrogenase by the high intracellular concentration of galactarate, along with a need for an additional energy supply for active transport of the dissociated anion out of the cell.…”

Section: Discussionmentioning

confidence: 74%

Metabolic Engineering of Fungal Strains for Conversion of d -Galacturonate to meso -Galactarate

Mojžita

Wiebe

Hilditch

et al. 2010

Appl Environ Microbiol

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D-Galacturonic acid can be obtained by hydrolyzing pectin, which is an abundant and low value raw material. By means of metabolic engineering, we constructed fungal strains for the conversion of D-galacturonate to meso-galactarate (mucate). Galactarate has applications in food, cosmetics, and pharmaceuticals and as a platform chemical. In fungi D- D-Galacturonate is the main component of pectin, an abundant and cheap raw material. Sugar beet pulp and citrus peel are both rich in pectin residues. At present, these residues are mainly used as cattle feed. However, since energy-consuming drying and pelletizing of the residues is required to prevent them from rotting, it is not always economical to process the residues, and it is desirable to find alternative uses.Various microbes which live on decaying plant material have the ability to catabolize D-galacturonate using various, completely different pathways (19). Eukaryotic microorganisms use a reductive pathway in which D-galacturonate is first reduced to L-galactonate by an NAD(P)H-dependent reductase (12,17). In the following steps a dehydratase, aldolase, and reductase convert the L-galactonate to pyruvate and glycerol (9,11,14).In Hypocrea jecorina (anamorph Trichoderma reesei) the gar1 gene codes for a strictly NADPH-dependent D-galacturonate reductase. In Aspergillus niger a homologue gene sequence, gar2, exists; however, a different gene, gaaA, is upregulated during growth on D-galacturonate containing medium (16). The gaaA codes for a D-galacturonate reductase with different kinetic properties than the H. jecorina enzyme, having a higher affinity toward D-galacturonate and using either NADH or NADPH as cofactor. It is not known whether gar2 codes for an active protein.Some bacteria, such as Agrobacterium tumefaciens or Pseudomonas syringae, have an oxidative pathway for D-galacturonate catabolism. In this pathway D-galacturonate is first oxidized to meso-galactarate (mucate) by an NAD-utilizing D-galacturonate dehydrogenase. Galactarate is then converted in the following steps to ␣-ketoglutarate. This route is sometimes called the ␣-ketoglutarate pathway (20). Galactarate can also be catabolized through the glycerate pathway (20). The products of this pathway are pyruvate and D-glycerate. These pathways have been described in prokaryotes, and it is not certain whether similar pathways also exist in fungi, some of which are able to metabolize galactarate.D-Galacturonate dehydrogenase (EC 1.1.1.203) has been described in Agrobacterium tumefaciens and in Pseudomonas syringae, and the enzymes from these organisms have been purified and characterized (3,6,22). Recently, the corresponding genes were also identified (4, 24). Both enzymes are specific for NAD as a cofactor but are not specific for the substrate. They oxidize D-galacturonate and D-glucuronate to meso-galactarate (mucate) and D-glucarate (saccharate), respectively. The reaction product is probably the hexaro-lactone which spontaneously hydrolyzes. The reverse reaction can only be observed at acidic ...

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Section: Discussionmentioning

confidence: 74%

Metabolic Engineering of Fungal Strains for Conversion of d -Galacturonate to meso -Galactarate

Mojžita

Wiebe

Hilditch

et al. 2010

Appl Environ Microbiol

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“…It has been reported that AA can also enter the cell by Fps1p-mediated facilitated diffusion. [34][35][36] However, no information on the relation between aquaglyceroporin Fps1p and PA could be found.…”

Section: Discussionmentioning

confidence: 89%

Acetate but not propionate induces oxidative stress in bakers’ yeastSaccharomyces cerevisiae

et al. 2011

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The influence of acetic and propionic acids on baker's yeast was investigated in order to expand our understanding of the effect of weak organic acid food preservatives on eukaryotic cells. Both acids decreased yeast survival in a concentration-dependent manner, but with different efficiencies. The acids inhibited the fluorescein efflux from yeast cells. The inhibition constant of fluorescein extrusion from cells treated with acetate was significantly lower in parental strain than in either PDR12 (ABC-transporter Pdr12p) or WAR1 (transcriptional factor of Pdr12p) defective mutants. The constants of inhibition by propionate were virtually the same in all strains used. Yeast exposure to acetate increased the level of oxidized proteins and the activity of antioxidant enzymes, while propionate did not change these parameters. This suggests that various mechanisms underlie the yeast toxicity by acetic and propionic acids. Our studies with mutant cells clearly indicated the involvement of Yap1p transcriptional regulator and de novo protein synthesis in superoxide dismutase up-regulation by acetate. The up-regulation of catalase was Yap1p independent. Yeast pre-incubation with low concentrations of H 2 O 2 caused cellular cross-protection against high concentrations of acetate. The results are discussed from the point of view that acetate induces a prooxidant effect in vivo, whereas propionate does not.

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“…Uptake of dicarboxylic acids in yeasts has been reported in several papers (4,9,11,12,26,28,32). It is believed that several yeast strains, such as Schizosaccharomyces pombe, Candida sphaerica, Candida utilis, and Hansenula anomala, can import dicarboxylic acids via a proton symport mechanism.…”

mentioning

confidence: 99%

pH-Dependent Uptake of Fumaric Acid in Saccharomyces cerevisiae under Anaerobic Conditions

Jamalzadeh

Verheijen

Heijnen

et al. 2012

Appl Environ Microbiol

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Microbial production of C 4 dicarboxylic acids from renewable resources has gained renewed interest. The yeast Saccharomyces cerevisiae is known as a robust microorganism and is able to grow at low pH, which makes it a suitable candidate for biological production of organic acids. However, a successful metabolic engineering approach for overproduction of organic acids requires an incorporation of a proper exporter to increase the productivity. Moreover, low-pH fermentations, which are desirable for facilitating the downstream processing, may cause back diffusion of the undissociated acid into the cells with simultaneous active export, thereby creating an ATP-dissipating futile cycle. In this work, we have studied the uptake of fumaric acid in S. cerevisiae in carbon-limited chemostat cultures under anaerobic conditions. The effect of the presence of fumaric acid at different pH values (3 to 5) has been investigated in order to obtain more knowledge about possible uptake mechanisms. The experimental results showed that at a cultivation pH of 5.0 and an external fumaric acid concentration of approximately 0.8 mmol · liter ؊1 , the fumaric acid uptake rate was unexpectedly high and could not be explained by diffusion of the undissociated form across the plasma membrane alone. This could indicate the presence of protein-mediated import. At decreasing pH levels, the fumaric acid uptake rate was found to increase asymptotically to a maximum level. Although this observation is in accordance with proteinmediated import, the presence of a metabolic bottleneck for fumaric acid conversion under anaerobic conditions could not be excluded.

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Transport of carboxylic acids in yeasts

Cited by 160 publications

References 174 publications

Metabolic Engineering of Fungal Strains for Conversion of d -Galacturonate to meso -Galactarate

Metabolic Engineering of Fungal Strains for Conversion of d -Galacturonate to meso -Galactarate

Acetate but not propionate induces oxidative stress in bakers’ yeastSaccharomyces cerevisiae

pH-Dependent Uptake of Fumaric Acid in Saccharomyces cerevisiae under Anaerobic Conditions

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