1887

Abstract

The physiological phenotype of was investigated for different genetic and environmental conditions of glucose repression through the quantification of fluxes in the central carbon metabolism using C-metabolic-flux analysis. The particular focus was the role of the carbon repressor CreA, which is the major regulatory protein mediating carbon repression in many fungal species, in the primary metabolism of . Batch cultivations were performed with a reference strain and a deletion mutant strain (Δ4) using [1-C]glucose as carbon source. The mutant strain was also grown on a mixture of [1-C]glucose and unlabelled xylose. Fractional enrichment data were measured by gas chromatography-mass spectrometry. A model describing the central metabolism of was used in combination with fractional enrichment data, and measurements of extracellular rates and biomass composition for the estimation of the metabolic fluxes. The -mutant strain showed a lower maximum specific growth rate than the reference strain when grown on glucose (0·11 and 0·25 h, respectively), whereas the specific growth rate of the mutant strain grown on the glucose/xylose mixture was identical to that on glucose (0·11 h). Different patterns and increased levels of extracellular polyols were observed both upon deletion of the gene and upon addition of xylose to the growth medium of the mutant strain. Concerning metabolic fluxes, the major change observed in the flux distribution of upon deletion of the gene was a 20 % decrease in the flux through the oxidative part of the pentose-phosphate pathway. Addition of xylose to the growth medium of the mutant resulted in an increase of about 40 % in the activity of the oxidative part of the pentose-phosphate pathway, as well as decreases in the fluxes through the Embden–Meyerhof–Parnas pathway and the tricarboxylic acid cycle (in the range of 20–30 %). The derepression of key pathways leads to alterations in the demands for cofactors, thereby imposing changes in the central metabolism due to the coupling of the many different reactions via the redox and energy metabolism of the cells.

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2005-07-01
2020-07-14
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