Investigation on the Metabolic Regulation of pgi gene knockout Escherichia coli by Enzyme Activities and Intracellular Metabolite Concentrations

• Published in: Malaysian Journal of Microbiology 2006-12, Vol.2 (2), p.24-31
• Main Authors: Aini, A. R., Shirai, Y., Hassan, M. A., Shimizu, K.
• Format: Article
• Language: English
• Subjects: Enzyme activity; Escherichia coli; Intracellular metabolite; Pgi mutant
• ISSN: 2231-7538; 1823-8262; 2231-7538
• DOI: 10.21161/mjm.220605

An integrated analysis of the cell growth characteristics, enzyme activities, intracellular metabolite concentrations was made to investigate the metabolic regulation of pgi gene knockout Escherichia coli based on batch culture and continuous culture which was performed at the dilution rate of 0.2h-1. The enzymatic study identified that pathways of pentose phosphate, ED pathway and glyoxylate shunt were all active in pgi mutant. The glycolysis enzymes i.e glyceraldehyde-3-phosphate dehydrogenase, fructose diphosphatase, pyruvate kinase, triose phosphate isomerase were down regulated implying that the inactivation of pgi gene reduced the carbon flux through glycolytic pathway. Meanwhile, the pentose phosphate pathway was active as a major route for intermediary carbohydrate metabolism instead of glycolysis. The pentose phosphate pathway generates most of the major reducing co-factor NADPH as shown by the increased of NADPH/NADP+ ratio in the mutant when compared with the parent strain. The fermentative enzymes such as acetate kinase and lactate dehydrogenase were down regulated in the mutant. Knockout of pgi gene results in the significant increase in the intracellular concentration of glucose-6-phosphate and decrease in the concentration of oxaloacetate. The slow growth rate of the mutant was assumed to be affected by the accumulation of glucose-6-phosphate and imbalance of NADPH reoxidation.