D‐Lactate production as a function of glucose metabolism in Saccharomyces cerevisiae

Abstract

Methylglyoxal, a reactive, toxic dicarbonyl, is generated by the spontaneous degradation of glycolytic intermediates. Methylglyoxal can form covalent adducts with cellular macromolecules, potentially disrupting cellular function. We performed experiments using the model organism Saccharomyces cerevisiae grown in media containing low, moderate, and high glucose concentrations to determine the relationship between glucose consumption and methylglyoxal metabolism. Normal growth experiments and glutathione depletion experiments showed that metabolism of methylglyoxal by log-phase yeast cultured aerobically occurred primarily through the glyoxalase pathway. Growth in high-glucose media resulted in increased generation of the methylglyoxal metabolite D-lactate and overall lower efficiency of glucose utilization as measured by growth rates. Cells grown in high-glucose media maintained higher glucose uptake flux than cells grown in moderate-glucose or low-glucose media. Computational modeling showed that increased glucose consumption may impair catabolism of triose phosphates as a result of an altered NAD+/NADH ratio.

Saccharomyces cerevisiae Forms d-2-Hydroxyglutarate and Couples Its Degradation to d-Lactate Formation via a Cytosolic Transhydrogenase

“…In our batch cultivations for example, in minimal media supplemented with 1% glucose, extracellular ethanol concentrations reached 122 and 133 mM in the wildtype strain and the dld3⌬ mutant, respectively, whereas the extracellular D-lactate concentrations remained below 400 M in the wild-type strain and the extracellular D-2HG concentrations below 140 M in the dld3⌬ mutant. In this context it is worth mentioning that, although D-lactate is so far considered as a metabolite specifically derived from methylglyoxal detoxification in yeast (58), the important drop in D-lactate levels measured in the dld3⌬ mutant strain in this study suggests that D-lactate actually derives mainly from the reduction of pyruvate that accompanies the newly identified transhydrogenase reaction catalyzed by Dld3 on D-2HG. As discussed below, rather than NADH recycling, the critical role of Dld3 may be mainly the reconversion of the useless and potentially toxic metabolite D-2HG to the important metabolic intermediate ␣-ketoglutarate.…”

Exploring the Arabidopsis sulfur metabolome

“…Dicarboxyethyl GSH has been proposed as an intermediate in detoxification of reactive aldehydes generated by oxidation of fatty acids (Singh et al ., ). Aldehydes, including sugars in their aldose conformation, are common targets of glutathionylation in animal and plant systems, for example in the glyoxylate pathway (Sousa Silva et al ., ; Stewart et al ., ). Thus, some of the predicted GS conjugates altered in the ggt4‐1 mutant may be related to sugar metabolism and involved in oxidative stress responses.…”

Transcriptomic response of Saccharomyces cerevisiae for its adaptation to sulphuric acid-induced stress

“…Methylglyoxal is produced in yeast by spontaneous b-elimination of DHAP produced by the glycolytic flux (Stewart et al 2013). Methylglyoxal is produced in yeast by spontaneous b-elimination of DHAP produced by the glycolytic flux (Stewart et al 2013).…”