Interactions between glucose metabolism and oxidative phosphorylations on respiratory‐competent Saccharomyces cerevisiae cells

Abstract

The purpose of this work was to analyze the interactions between oxidative phosphorylations and glucose metabolism on yeast cells aerobically grown on lactate as carbon source and incubated in a resting cell medium. On such respiratory-competent yeast cells, four different metabolic steady states have particularly been studied: (a) glucose feeding under anaerobiosis, (b) ethanol supply under aerobiosis, (c) glucose supply under aerobiosis and (d) glucose plus ethanol under aerobiosis. For each condition, we measured: (a) the cellular ATP/ADP ratio and NADH content sustained under these conditions, (b) the glucose consumption rate (glucose conditions) and the respiratory rate (aerobic conditions).Under aerobic conditions, when ethanol is used as substrate, the ATP/ADP ratio and NADH level are very high as compared with glucose feeding. However, the rate of oxygen consumption is similar under both conditions. The main observation is a large increase in the respiratory rate when both glucose and ethanol are added. This increase corresponds to an ATP/ADP ratio and a NADH level lower than those observed with ethanol but higher than those with glucose. Therefore the response of the respiratory rate to the ATP/ADP ratio depends on the redox potential. We studied the way in which the ATP-consuming activity was increased under glucose + ethanol conditions. By NMR experiments, it appears that neither the futile cycle at the level of the phosphofructo-lkinase/fructo-l,6-bisphosphatase couple nor the synthesis of carbohydrate stores could account for the increase in oxidative phosphorylation. However, it is shown that, in the presence of glucose + ethanol, ATP consumption is strongly stimulated. It is hypothesized that this consumption is essentially due to the combination of the well-known plasma membrane proton-ATPase activation by glucose and the high phosphate potential due to oxidative ethanol metabolism. While it is well documented that oxidative phosphorylations inhibit the glycolytic flux, i.e. the Pasteur effect, we clearly show in this work that the glycolytic pathway limits the ability of mitochondria to maintain a cellular phosphate potential.Studies on isolated mitochondria have demonstrated that the ATP synthesis flux coupled to respiratory rate is controlled by the intramitochondrial phosphate potential value according to both the presence and the nature of the intra-or extramatricial ADP-regenerating system (Kuster et al

The Trehalose Pathway Regulates Mitochondrial Respiratory Chain Content through Hexokinase 2 and cAMP in Saccharomyces cerevisiae

“…Taken together, these results indicate that besides the thermodynamic link between glycolysis and mitochondrial respiration (i.e. the cytosolic ATP/ADP and NADH/NADϩ ratio), a kinetic control of oxidative phosphorylation activity is exerted by the level of glycolytic sugar phosphates (18,23). This raises the question of a possible direct or indirect regulation of oxidative phosphorylation by the trehalose synthesis pathway.…”

Dynamical Remodeling of the Transcriptome during Short-Term Anaerobiosis in Saccharomyces cerevisiae: Differential Response and Role of Msn2 and/or Msn4 and Other Factors in Galactose and Glucose Media

“…Here we find a 40% reduction in growth rate when respiration is inhibited by either antimycin A or anoxia in cells grown in galactose medium ( Table 2). The abrupt cessation of respiration will lead to a rapid, albeit transient change in the phosphorylation state of the purine nucleotide pool before compensatory mechanisms are activated (7,19). A rapid but more sustained increase in cellular redox potential is also expected (82) yet should be similar, although not identical, in the two media.…”

Role of the non‐respiratory pathways in the utilization of molecular oxygen by Saccharomyces cerevisiae

“…15,21,64,84,153,161,197 In contrast, to our knowledge, the respective contributions of the numerous non-respiratory pathways to the overall molecular oxygen consumption have not yet been reviewed. Moreover, the activity, regulation and physiological roles of non-respiratory oxygen utilization pathways remain often unclear.…”

“…It results from kinetic regulations along the glycolytic pathway and thermodynamic constraints due to the competition between glycolysis and oxidative phosphorylation for ADP and inorganic phosphate (Pi) and for reducing equivalents. 21,64,161 Oxygen utilization by S. cerevisiae: characteristics…”