Metabolic flux response to phosphoglucose isomerase knock-out in Escherichia coli and impact of overexpression of the soluble transhydrogenase UdhA

Blocking glycolytic breakdown of glucose by inactivation of phosphoglucose isomerase (Pgi) in Escherichia coli led to a greatly reduced maximum specif ic growth rate. Examination of the operational catabolic pathways and their flux ratios using [U-13C6]glucose-labeling experiments and metabolic flux ratio analysis provide evidence for the pentose phosphate (PP) pathway as t he primary route of glucose catabolism in the knock-out mutant. The resulti ng extensive flux through the PP pathway disturbs apparently the reducing p ower balance, since overexpression of the recently identified soluble trans hydrogenase UdhA improves significantly the growth rate of the Pgi mutant. The presented results provide First evidence that UdhA restores the cellula r redox balance by catalyzing electron transfer from NADPH to NADH. (C) 200 1 Federation of European Microbiological Societies. Published by Elsevier S cience B.V. All rights reserved.