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Atypical glycolysis in Clostridium thermocellum
Jilai Zhou1, Daniel G Olson, D Aaron Argyros
1Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA.
Applied and Environmental Microbiology
|February 26, 2013
Summary
Clostridium thermocellum glycolysis uniquely uses GTP and pyrophosphate (PPi), not ATP, for key steps. This anaerobic bacterium requires alternative PPi generation beyond biosynthesis for cellobiose fermentation.
Area of Science:
- Biochemistry
- Microbiology
- Metabolic Engineering
Background:
- Glycolysis in anaerobic heterotrophs typically relies on ATP and pyrophosphate (PPi).
- Understanding cofactor specificities in Clostridium thermocellum is crucial for its industrial applications.
Purpose of the Study:
- To elucidate the cofactor specificities of glycolytic enzymes in Clostridium thermocellum.
- To investigate the source of pyrophosphate (PPi) required for glycolysis in this organism.
Main Methods:
- Enzyme activity assays using cellobiose-grown cells.
- Gene deletion studies of pyruvate phosphate dikinase (ppdk).
- Metabolic network analysis and experiments with washed-cell suspensions.
Main Results:
- Glucokinase utilized GTP, and phosphofructokinase showed PPi-linked activity.
- Pyruvate formation occurred via a malate shunt involving GDP-linked PEP carboxykinase, not pyruvate kinase or ppdk.
- Significant PPi generation from ATP/GTP hydrolysis is necessary, beyond biosynthetic needs.
Conclusions:
- C. thermocellum glycolysis exhibits unique cofactor dependencies, consuming GTP and requiring substantial PPi generation.
- The malate shunt is critical for pyruvate formation in this bacterium.
- Alternative PPi generation mechanisms are essential for anaerobic fermentation in C. thermocellum.
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