Glucose-PTS Involvement in Maltose Metabolism by Streptococcus mutans
Yutaka Sato1, Kazuko Okamoto-Shibayama, Toshifumi Azuma
1Department of Biochemistry, Tokyo Dental College.
The Bulletin of Tokyo Dental College
|June 19, 2015
Summary
Streptococcus mutans utilizes maltose via the MalQ enzyme. Unexpectedly, glucose phosphorylation occurs through the mannose phosphotransferase system (PTS), not glucokinase, in this oral bacterium.
Area of Science:
- Microbiology
- Bacterial Metabolism
- Oral Microbiology
Background:
- Streptococcus mutans metabolizes starch-derived maltose using the MalQ protein (4-alpha-glucanotransferase).
- Glucose produced from maltose catabolism typically enters glycolysis via phosphorylation.
- A glucokinase gene-inactivated mutant (glk mutant) still grew on maltose, suggesting an alternative glucose phosphorylation pathway.
Purpose of the Study:
- To investigate the role of the phosphoenolpyruvate-dependent phosphotransferase system (PTS) in maltose catabolism.
- To test the hypothesis that glucose is released extracellularly and re-transported via PTS.
- To elucidate the metabolic fate of maltose in Streptococcus mutans.
Main Methods:
- Enzyme-linked photometrical method to detect extracellular glucose.
- Monitoring absorbance changes at 340 nm in bacterial supernatant.
- Utilizing Streptococcus mutans mutants with inactivated glucokinase (glk) and mannose PTS genes (manLM).
Main Results:
- A significant amount of glucose was detected in the extracellular fluid of a glk, manLM double mutant.
- This indicates that glucose, derived from maltose, can be released and re-enter the cell.
- The mannose PTS (manLMN genes) facilitates high-affinity glucose transport and phosphorylation.
Conclusions:
- The glucokinase (glk) and mannose PTS (manLMN) genes are involved in maltose catabolism in Streptococcus mutans.
- This highlights the metabolic flexibility of S. mutans in utilizing available carbon sources.
- Multiple pathways for energy source metabolism are significant in the oral environment.
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