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Control of glycolytic flux in Zymomonas mobilis by glucose 6‐phosphate dehydrogenase activity

Control of glycolytic flux in Zymomonas mobilis by glucose 6‐phosphate dehydrogenase activity 10.1002/(SICI)1097-0290(19960720)51:2<190::AID-BIT8>3.3.CO;2-L Glycolytic genes in Zymomonas mobilis are highly expressed and constitute half of the cytoplasmic protein. The first four genes (glf, zwf, edd, glk) in this pathway form an operon encoding a glucose permease, glucose 6‐phosphate dehydrogenase (G6‐P dehydrogenase), 6‐phosphogluconate dehydratase, and glucokinase, respectively. Each gene was overexpressed from a tac promoter to investigate the control of glycolysis during the early stages of batch fermentation when flux (qCO2) is highest. Almost half of flux control appears to reside with G6‐P dehydrogenase (CJG6‐P dehydrogenase = 0.4). Although Z. mobilis exhibits one of the highest rates of glycolysis known, recombinants with elevated G6‐P dehydrogenase had a 10% to 13% higher glycolytic flux than the native organism. A small increase in flux was also observed for recombinants expressing glf. Results obtained did not allow a critical evaluation of glucokinase and this enzyme may also represent an important control point. 6‐Phosphogluconate dehydratase appears to be saturating at native levels. With constructs containing the full operon, growth rate and flux were both reduced, complicating interpretations. However, results obtained were also consistent with G6‐P dehydrogenase as a primary site of control. Flux was 17% higher in operon constructs which exhibited a 17% increase in G6‐P dehydrogenase specific activity, relative to the average of other operon constructs which contain a frameshift mutation in zwf. It is unlikely that all flux control residues solely in G6‐P dehydrogenase (calculated CJG6‐P dehydrogenase = 1.0) although these results further support the importance of this enzyme. As reported in previous studies, changes in flux were not accompanied by changes in growth rate providing further evidence that ATP production does not limit biosynthesis in rich complex medium. © 1996 John Wiley & Sons, Inc. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Biotechnology and Bioengineering Wiley

Control of glycolytic flux in Zymomonas mobilis by glucose 6‐phosphate dehydrogenase activity

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References (32)

Publisher
Wiley
Copyright
Copyright © 1996 John Wiley & Sons, Inc.
ISSN
0006-3592
eISSN
1097-0290
DOI
10.1002/(SICI)1097-0290(19960720)51:2<190::AID-BIT8>3.0.CO;2-E
pmid
18624328
Publisher site
See Article on Publisher Site

Abstract

10.1002/(SICI)1097-0290(19960720)51:2<190::AID-BIT8>3.3.CO;2-L Glycolytic genes in Zymomonas mobilis are highly expressed and constitute half of the cytoplasmic protein. The first four genes (glf, zwf, edd, glk) in this pathway form an operon encoding a glucose permease, glucose 6‐phosphate dehydrogenase (G6‐P dehydrogenase), 6‐phosphogluconate dehydratase, and glucokinase, respectively. Each gene was overexpressed from a tac promoter to investigate the control of glycolysis during the early stages of batch fermentation when flux (qCO2) is highest. Almost half of flux control appears to reside with G6‐P dehydrogenase (CJG6‐P dehydrogenase = 0.4). Although Z. mobilis exhibits one of the highest rates of glycolysis known, recombinants with elevated G6‐P dehydrogenase had a 10% to 13% higher glycolytic flux than the native organism. A small increase in flux was also observed for recombinants expressing glf. Results obtained did not allow a critical evaluation of glucokinase and this enzyme may also represent an important control point. 6‐Phosphogluconate dehydratase appears to be saturating at native levels. With constructs containing the full operon, growth rate and flux were both reduced, complicating interpretations. However, results obtained were also consistent with G6‐P dehydrogenase as a primary site of control. Flux was 17% higher in operon constructs which exhibited a 17% increase in G6‐P dehydrogenase specific activity, relative to the average of other operon constructs which contain a frameshift mutation in zwf. It is unlikely that all flux control residues solely in G6‐P dehydrogenase (calculated CJG6‐P dehydrogenase = 1.0) although these results further support the importance of this enzyme. As reported in previous studies, changes in flux were not accompanied by changes in growth rate providing further evidence that ATP production does not limit biosynthesis in rich complex medium. © 1996 John Wiley & Sons, Inc.

Journal

Biotechnology and Bioengineering – Wiley

Published: Jul 20, 1996

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