Interaction of Streptococcus mutans glucosyltransferases with teichoic acids

Area of Science:

• Microbiology
• Biochemistry

Background:

• Streptococcus mutans is a key pathogen in dental caries.
• Glucosyltransferases (GTFs) are essential enzymes for S. mutans virulence, synthesizing glucans from sucrose.
• Lipoteichoic acid (LTA) is a major cell wall component of Gram-positive bacteria.

Purpose of the Study:

• To investigate the inhibitory effects of purified lipoteichoic acid on Streptococcus mutans GS5 glucosyltransferase (GTF) activity.
• To determine the role of LTA in the in vitro colonization of smooth surfaces by S. mutans.
• To elucidate the mechanism of LTA-GTF interaction and its implications for enzyme binding and aggregation.

Main Methods:

• Purified lipoteichoic acid was used to inhibit purified GTF enzymes from S. mutans GS5.
• In vitro assays measured sucrose-dependent colonization of smooth surfaces.
• Enzyme kinetics were analyzed to determine the type of inhibition.
• Deacylated LTAs were used to assess the role of fatty acid components.
• High-molecular-weight enzyme complexes were analyzed.

Main Results:

• Purified lipoteichoic acid inhibited both water-soluble and insoluble glucan-synthesizing GTF activities from S. mutans GS5.
• LTA significantly reduced sucrose-dependent colonization of smooth surfaces by S. mutans GS5 in vitro.
• Inhibition of soluble GTF synthesis by LTA was competitive with respect to sucrose and dextran T10.
• Deacylated LTAs did not inhibit GTF activity but interacted with the enzymes, protecting against heat inactivation and inducing complex formation.
• Polyglycerophosphate was detected in high-molecular-weight GTF aggregates, suggesting teichoic acid involvement.
• GTF activity also bound to Lactobacillus casei and Lactobacillus fermentum, which contain polyglycerophosphate teichoic acids.

Conclusions:

• Lipoteichoic acid acts as a competitive inhibitor of Streptococcus mutans glucosyltransferases.
• LTA plays a significant role in reducing bacterial colonization by interfering with GTF activity.
• Teichoic acid-GTF interactions are important for enzyme binding to the cell surface and the formation of enzyme aggregates in culture fluids.