Supply of Gibbs free energy and precursors are vital for cellular function and cell metabolism have evolved to be tightly regulated to balance their supply and consumption. Precursors and Gibbs free energy are generated in the central carbon metabolism (CCM), and fluxes through these pathways are precisely regulated. However, how fluxes through CCM pathways are affected by posttranslational modification and allosteric regulation remains poorly understood. Here, we integrated multi-omics data collected under nine different chemostat conditions to explore how fluxes in the CCM are regulated in the yeast Saccharomyces cerevisiae . We deduced a pathway- and metabolism-specific CCM flux regulation mechanism using hierarchical analysis combined with mathematical modeling. We found that increased glycolytic flux associated with an increased specific growth rate was accompanied by a decrease in flux regulation by metabolite concentrations, including the concentration of allosteric effectors, and a decrease in the phosphorylation level of glycolytic enzymes.

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The Crabtree effect in the yeast, Saccharomyces cerevisiae, has been extensively studied, but only few studies have analyzed the dynamic conditions across the critical specific growth rate where the Crabtree effect sets in. Here, we carried out a multi-omics analysis of S. cerevisiae undergoing a specific growth rate transition from 0.2 h−1 to 0.35 h−1. The extracellular metabolome, the transcriptome and the proteome were analyzed in an 8-h transition period after the specific growth rate shifted from 0.2 h−1 to 0.35 h−1. The changing trends of both the transcriptome and proteome were analyzed using principal component analysis, which showed that the transcriptome clustered together after 60 min, while the proteome reached steady-state much later. Focusing on central carbon metabolism, we analyzed both the changes in the transcriptome and proteome, and observed an interesting changing pattern in the tricarboxylic acid (TCA) pathway, which indicates an important role for citric acid shuttling across the mitochondrial membrane for α-ketoglutarate accumulation during the transition from respiratory to respiro-fermentative metabolism. This was supported by a change in the oxaloacetate and malate shuttle. Together, our findings shed new light into the onset of the Crabtree effect in S. cerevisiae.

Energy metabolism is central for cellular function and has therefore evolved to be tightly regulated such that energy production can be balanced to energy demand. Energy is being produced in the central carbon metabolism (CCM) and even though there has been extensive studies on how fluxes through the different pathways in this part of metabolism are regulated. There is little understanding of how fluxes are affected by posttranslational modifications and by allosteric regulators. Here we integrated multi-omics data (intracellular metabolome, extracellular metabolome, proteome, phosphoproteome, and fluxome) under 9 different chemostat conditions for building a mathematical model that could map functional regulatory events (FREs) in the Saccharomyces cerevisiae. Using hierarchical analysis combined with the mathematical model, we observed pathway and metabolism-specific flux regulation mechanisms in the CCM. We also found that the glycolytic flux increased with specific growth rate, and this increase was accompanied by a decrease of both metabolites derived FREs and protein phosphorylation level.