MATHEMATICAL-MODEL FOR THE DETERMINATION OF METABOLITE FLUXES IN SACCHAROMYCES-CEREVISIAE

We present a mathematical model to determine the absolute values of flux leading to the formation and the disappearance of ethanol and acetyl-CoA in Saccharomyces cerevisiae under repressed state conditions. Cells were fed with [1-C-13]glucose with or without unlabeled ethanol. Addition of unlabeled ethanol induces a modulation, with time, of the fractional enrichment of this compound. This experimental approach allows us to obtain the relationships between metabolite fluxes and the other parameters (fractional enrichment, concentration and time). Metabolites are analysed by H-1-, C-13-NMR and enzymatic methods. The validity of the present model is supported by the data obtained from similar experiments using unlabeled ethanol as a sole carbon source and non-NMR techniques.