Abstract: The yeast Saccharomyces cerevisiae is able to adapt its metabolism to grow on different carbon sources and to shift to non-fermentative growth on C2 or C3 carbon sources (ethanol, acetate, or glycerol) through the activation of gluconeogenesis. Here, we studied the response to the deletion of the glycolytic and gluconeogenic gene GPM1, encoding for phosphoglycerate mutase. It was previously shown that a S. cerevisiae strain with non-functional copies of GPM1 can only grow when glycerol and ethanol are both present as carbon sources, whilst addition of glucose was shown to strongly inhibit growth. It was suggested that glycerol is needed to feed gluconeogenesis whilst ethanol is required for respiration. Here, we studied the physiological response of the GPM1 knock-out mutant through fermentation and transcriptome analysis. Furthermore, we compared the physiological results with those obtained through simulations using a genome-scale metabolic model, showing that glycerol is only needed in small amounts for growth. Our findings strongly suggest a severely impaired growth ability of the knock-out mutant, which presents increased transcript levels of genes involved in the pentose phosphate pathway and in the glyoxylate shunt. These results indicate an attempt to compensate for the energy imbalance caused by the deletion of the glycolytic/gluconeogenic gene within the mutant.