Glucose-6-phosphate-dependent pyruvate kinase in Streptococcus mutans

Area of Science:

• Biochemistry
• Microbiology
• Enzymology

Background:

• Pyruvate kinase is a key enzyme in glycolysis, catalyzing the final step.
• Understanding pyruvate kinase in oral streptococci is crucial for studying carbohydrate metabolism in these bacteria.

Purpose of the Study:

• To characterize the kinetic properties and cofactor requirements of pyruvate kinase from Streptococcus mutans JC 2.
• To compare the pyruvate kinase characteristics across different species of oral streptococci.

Main Methods:

• Enzyme assays were performed to determine substrate specificity and cofactor dependency.
• Kinetic parameters were analyzed under varying conditions.
• Comparative analysis of enzyme activity across different bacterial strains.

Main Results:

• Streptococcus mutans JC 2 pyruvate kinase demonstrated an absolute requirement for glucose-6-phosphate as a substrate.
• The enzyme was inhibited by inorganic phosphate and required divalent cations (Mg2+ or Mn2+) and monovalent cations (K+ or NH4+).
• Pyruvate kinases from S. mutans FIL, S. mutans E 49, Streptococcus bovis, and Streptococcus salivarius also showed glucose-6-phosphate dependency, while Streptococcus sanguis exhibited fructose-1,6-diphosphate activation.

Conclusions:

• Pyruvate kinase from Streptococcus mutans JC 2 has distinct regulatory properties, emphasizing glucose-6-phosphate dependency.
• This substrate specificity is conserved among several oral streptococcal species, suggesting a common metabolic pathway.
• The differing enzyme characteristics in Streptococcus sanguis highlight potential variations in glycolytic regulation within the genus Streptococcus.