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Characterization of glutamine transport in Streptococcus mutans
S G Dashper1, P F Riley, E C Reynolds
1Biochemistry and Molecular Biology Unit, School of Dental Science, University of Melbourne, Australia.
Oral Microbiology and Immunology
|June 1, 1995
Summary
Streptococcus mutans utilizes an ATP-driven system for glutamine transport, not proton motive force. This specific transporter, active at pH 6.0-7.0, converts glutamine to glutamate, suggesting it
Area of Science:
- Microbiology
- Cellular Physiology
Background:
- Streptococcus mutans is a key cariogenic bacterium.
- Understanding nutrient transport is crucial for studying bacterial metabolism.
Purpose of the Study:
- To elucidate the mechanism and characteristics of glutamine transport in Streptococcus mutans.
Main Methods:
- Kinetic analysis of glutamine uptake in energized and de-energized cells.
- Investigation of proton motive force (PMF) influence on transport.
- Assessment of transport activity across different pH levels.
- Competitive inhibition studies with related amino acids.
- Analysis of intracellular glutamine metabolism using HPLC.
Main Results:
- Glutamine transport follows Michaelis-Menten kinetics, with distinct Vmax and Kt values for energized and de-energized cells.
- Transport is not driven by PMF; evidence suggests ATP hydrolysis as the energy source.
- Optimal transporter activity occurs between pH 6.0 and 7.0.
- Transport is specific for glutamine, with no competitive inhibition by asparagine, glutamate, or aspartate.
- Intracellular glutamine is rapidly converted to glutamate, indicating glutaminase activity.
Conclusions:
- Glutamine transport in S. mutans is an active, ATP-dependent process.
- The system is specific for glutamine and plays a role in nitrogen acquisition.
- Intracellular conversion to glutamate suggests glutamine serves as a nitrogen source for the cell.