Phosphoenolpyruvate-dependent glucose phosphotransferase activity in Streptococcus mitis ATCC 903

Area of Science:

• Microbiology
• Biochemistry
• Oral Health

Background:

• Streptococcus mitis is a common oral bacterium.
• Understanding bacterial sugar transport mechanisms is crucial for oral health research.
• Phosphotransferase systems (PTS) are key for bacterial carbohydrate metabolism.

Purpose of the Study:

• To investigate the presence and characteristics of a glucose phosphotransferase system in Streptococcus mitis.
• To determine the kinetic properties of this system using a glucose analogue.
• To assess the system's activity in different cellular states and in dental plaque.

Main Methods:

• Enzyme assays using decryptified and intact Streptococcus mitis cells.
• Kinetic analysis with 2-deoxyglucose (2DG) as a substrate.
• Chromatographic analysis of accumulated phosphorylated sugars.
• Investigation of enzyme activity in freshly collected dental plaque samples.

Main Results:

• A constitutive phosphoenolpyruvate (PEP)-dependent glucose phosphotransferase system was identified in Streptococcus mitis.
• The system exhibited saturation kinetics with an apparent Km of 0.4 mM for 2-deoxyglucose (2DG).
• Intact cells accumulated 2DG and its phosphorylated derivative, 2DG-6-phosphate, demonstrating active transport and phosphorylation. Sodium fluoride inhibited activity when 2-phosphoglycerate was the energy source, indicating PEP dependency.
• PEP-dependent glucose phosphotransferase activity was confirmed in freshly collected dental plaque.

Conclusions:

• Streptococcus mitis utilizes a PEP-dependent phosphotransferase system for glucose uptake and phosphorylation.
• This system is active in both isolated cells and the complex environment of dental plaque.
• The findings contribute to understanding carbohydrate metabolism in oral streptococci and its implications for oral ecology.