Insoluble glucan synthesis by Streptococcus mutans serotype c strains

Area of Science:

• Microbiology
• Biochemistry
• Enzymology

Background:

• Streptococcus mutans produces glucans crucial for dental plaque formation.
• Dextransucrase and mutansynthetase are key enzymes in glucan synthesis.
• Understanding their distinct roles is vital for controlling cariogenic biofilms.

Purpose of the Study:

• To purify and characterize dextransucrase and mutansynthetase from Streptococcus mutans GS-5.
• To investigate the influence of ammonium ions on glucan synthesis.
• To differentiate between the two enzymes based on their properties and activity.

Main Methods:

• Enzyme purification using ammonium sulfate precipitation and chromatofocusing.
• Glucan synthesis assays under varying conditions (e.g., presence of ammonium ions, primer).
• Enzyme characterization including molecular weight determination, isoelectric focusing, and antibody cross-reactivity.

Main Results:

• Dextransucrase synthesized water-insoluble glucans in the presence of 1.5 M ammonium sulfate, increasing alpha-1,3 linkages.
• Mutansynthetase synthesized primer-dependent insoluble glucan, with activity decreasing in the presence of ammonium ions.
• Dextransucrase and mutansynthetase were distinguished by higher molecular weight, lower isoelectric point, and lack of antibody cross-reactivity for mutansynthetase.

Conclusions:

• Ammonium ions significantly alter the product profile of dextransucrase towards insoluble glucan synthesis.
• Dextransucrase and mutansynthetase are distinct enzymes with different characteristics and roles in insoluble glucan production.
• These findings contribute to understanding the mechanisms of glucan synthesis by Streptococcus mutans serotype c.