Quantitative analysis of the regulation scheme of invertase expression in Saccharomyces cerevisiae

Abstract

In Saccharomyces cerevisiae, the expression of invertase, which is the hydrolyzing enzyme of sucrose, is controlled by the presence of monosaccharides, such as glucose and fructose, and referred to as carbon catabolite repression. To date, efforts have been made to identify the mechanism by which cells sense extracellular monosaccharide concentrations and trigger the genes involved in the repression pathway. The aim of the present work was to quantitatively investigate the cellular regulation of invertase expression in the wild-type strain S. cerevisiae CEN.PK113-7D during batch growth containing mixed sugar substrates under different initial conditions. Because of the high frequency and accurate online analysis of multiple components, a tight control of invertase expression could be observed, and threshold concentrations of the monosaccharides for derepression could be determined to 0.5 gl(-1) for glucose and 2 gl(-1) for fructose. Also, the existence of a hitherto undescribed regulatory state, in which cells regulate invertase expression very precisely and operate over long periods at monosaccharide concentrations lower than the above thresholds, could be demonstrated. All experimental observations could be summarized in a formulation of the cellular regulation scheme of invertase expression. A simple kinetic model could show that the regulation scheme explains the observed behavior very well. Additionally, the model was able to explain consequences of the regulation on the global metabolism.

Sucrose Fermentation by <i>Saccharomyces cerevisiae</i> Lacking Hexose Transport

“…While the former mRNA is repressed by high concentrations of its hydrolysis products (glucose and fructose), the intracellular invertase is expressed constitutively. Finally, it has recently become evident that effi cient invertase expression requires low levels of glucose in the medium [Ozcan et al, 1997;Dynesen et al, 1998;Herwing et al, 2001].…”

Production of thermostable invertases by Aspergillus caespitosus under submerged or solid state fermentation using agroindustrial residues as carbon source

“…The acidic form has cell-wall or vacuolar localization and it is evolutionary related to yeast and bacterial invertases (28), differing of neutral and alkaline isoforms that are found on the cytosol (33). In yeast, the gene Suc 2 encodes two different invertases, a glycosilated form located in periplasmic space and a non-glycosilated form situated in the cytosol (12).…”

“…Invertase is classified in the GH32 family of glycoside hydrolases, that includes over 370 members (2) and has been reported in plant (28), bacteria (34), yeast (4,12) and filamentous fungi, as Aspergillus ochraceus (11), Aspergillus niger (24), Aspergillus japonicus (7) and Thermomyces lanuginosus (6).…”

Kinetics of improved extracellular ?-d-fructofuranosidase fructohydrolase production by a derepressed Saccharomyces cerevisiae

“…Thermodynamic parameters indicated that activation enthalpy of FFH formation by EMS-II (DH = 33AE55 ± 4AE2 kJ mol )1 ) was lower than that of its wild parent. The activation entropy of thermal inactivation by mutant cells (-297AE20 ± 12 J mol )1 K )1 ) was very low and comparable with that for invertase production by a thermotolerant yeast (Herwig et al 2001) which reflected that the cell system exerts protection against thermal inactivation of FFH.…”

“…Some reports have appeared on the mechanism of catabolic inhibition and regulation scheme of FFH expression in yeast, but did not yield a viable strain with enhanced enzyme productivity (Elorza et al 1977;Silveira et al 2000;Herwig et al 2001). Traditional methods for strain improvement, such as ultraviolet (UV) radiations or use of alkylating agents like N-methyl N-nitro N-nitroso guanidine (NG) to obtain mutants have proved successful when followed by suitable selection and screening of the survivors for FFH production (Weber and Roitsch 2003).…”