Inactivation of cell-associated fructosyltransferase in Streptococcus salivarius

Area of Science:

• Microbiology
• Enzymology
• Biochemistry

Background:

• Fructosyltransferase (FTase) is a key enzyme in Streptococcus salivarius.
• Understanding FTase regulation is crucial for studying bacterial metabolism and biofilm formation.

Purpose of the Study:

• To investigate the regulation and inactivation mechanisms of cell-associated fructosyltransferase (FTase) in Streptococcus salivarius ATCC 25975.
• To identify factors influencing FTase activity during bacterial growth and under non-growing conditions.

Main Methods:

• Enzyme activity assays were performed on cell-associated and released FTase.
• Inactivation studies involved incubating cells under various conditions (temperature, buffer composition, presence of metal ions and amino acids).
• Protein analysis using polyacrylamide gel electrophoresis (PAGE) was employed to compare active and inactivated enzyme preparations.

Main Results:

• 95% of FTase activity was cell-associated in stationary phase, with a 92% decrease in specific activity within 15 minutes of inoculation.
• FTase was resynthesized during exponential growth. Copper ions (Cu2+) induced rapid inactivation (80-95% loss), preventable by histidine, cysteine, or Ca2+.
• FTase inactivation was linked to the loss of specific protein bands, suggesting proteolytic degradation or conformational changes.

Conclusions:

• Cell-associated FTase in Streptococcus salivarius is subject to rapid inactivation upon entering fresh medium, but is subsequently resynthesized.
• Copper ions play a significant role in FTase inactivation, which can be mitigated by specific amino acids and calcium.
• The inactivation process involves the loss of specific protein components, indicating a complex regulatory mechanism.