Control of the Glycolytic Flux in Saccharomyces cerevisiae Grown at Low Temperature

Abstract

Growth temperature has a profound impact on the kinetic properties of enzymes in microbial metabolic networks. Activities of glycolytic enzymes in Saccharomyces cerevisiae were up to 7.5-fold lower when assayed at 12°C than at 30°C. Nevertheless, the in vivo glycolytic flux in chemostat cultures (dilution rate: 0.03 h-1) grown at these two temperatures was essentially the same. To investigate how yeast maintained a constant glycolytic flux despite the kinetic challenge imposed by a lower growth temperature, a systems approach was applied that involved metabolic flux analysis, transcript analysis, enzyme activity assays, and metabolite analysis. Expression of hexose-transporter genes was affected by the growth temperature, as indicated by differential transcription of five HXT genes and changed zero trans-influx kinetics of [14C]glucose transport. No such significant changes in gene expression were observed for any of the glycolytic enzymes. Fermentative capacity (assayed off-line at 30°C), which was 2-fold higher in cells grown at 12°C, was therefore probably controlled predominantly by glucose transport. Massive differences in the intracellular concentrations of nucleotides (resulting in an increased adenylate energy charge at low temperature) and glycolytic intermediates indicated a dominant role of metabolic control as opposed to gene expression in the adaptation of glycolytic enzyme activity to different temperatures. In evolutionary terms, this predominant reliance on metabolic control of a central pathway, which represents a significant fraction of the cellular protein of the organism, may be advantageous to limit the need for protein synthesis and degradation during adaptation to diurnal temperature cycles. © 2007 by The American Society for Biochemistry and Molecular Biology, Inc.