C. Herwig et al., Quantitative analysis of the regulation scheme of invertase expression in Saccharomyces cerevisiae, BIOTECH BIO, 76(3), 2001, pp. 247-258
In Saccharomyces cerevisiae, the expression of invertase, which is the hydr
olyzing enzyme of sucrose, is controlled by the presence of monosaccharides
, such as glucose and fructose, and referred to as carbon catabolite repres
sion. To date, efforts have been made to identify the mechanism by which ce
lls sense extracellular monosaccharide concentrations and trigger the genes
involved in the repression pathway. The aim of the present work was to qua
ntitatively investigate the cellular regulation of invertase expression in
the wild-type strain S. cerevisiae CEN.PK113-7D during batch growth contain
ing mixed sugar substrates under different initial conditions.
Because of the high frequency and accurate online analysis of multiple comp
onents, a tight control of invertase expression could be observed, and thre
shold concentrations of the monosaccharicles for derepression could be dete
rmined to 0.5 gl(-1) for glucose and 2 gl(-1) for fructose. Also, the exist
ence of a hitherto undescribed regulatory state, in which cells regulate in
vertase expression very precisely and operate over long periods at monosacc
haride concentrations lower than the above thresholds, could be demonstrate
d. All experimental observations could be summarized in a formulation of th
e cellular regulation scheme of invertase expression. A simple kinetic mode
l could show that the regulation scheme explains the observed behavior very
well. Additionally, the model was able to explain consequences of the regu
lation on the global metabolism. (C) 2001 John Wiley & Sons, Inc.