Metabolic flux analysis of Saccharomyces cerevisiae grown on glucose, glycerol or acetate by [formula omitted]-labeling experiments

Abstract

A hybrid type of computer program was developed for the estimation of intracellular metabolic fluxes based on 13 C -labeling experiment and the measurement of the signals of two-dimensional nuclear magnetic resonance (NMR) spectroscopy of proteinogenic amino acids. The continuous cultures of Saccharomyces cerevisiae were conducted at the dilution rate of 0.1 h −1 with different carbon sources such as glucose, glycerol or acetate labeled by 13 C . The effects of different carbon sources on the intracellular metabolic flux distribution (MFD) were investigated using the program developed. Some of the enzyme activities were also measured to ascertain the results of MFD. It was found that the pyruvate carboxylase instead of PEP carboxylase play the main role as anaplerotic reaction for the case of glucose and glycerol used as carbon sources. It was also found that the pathways via PEP carboxykinase (pck) and malic enzyme as well as glyoxylate shunt were used to a large extent for the assimilation of acetate. The general direction of reaction catalyzed by transketolase 2 reverses and the intermediate metabolite ribulose-5-phosphate and erythrose-4-phosphate were mainly produced by transaldolase and transketolase reactions during growth on acetate.