Biochemical mechanisms of enhanced inhibition of fluoride on the anaerobic sugar metabolism by Streptococcus sanguis

The effect of fluoride on acid production by Streptococcus sanguis ATCC 10556 was compared under anaerobic and aerobic conditions. The rate of acid production under constant-pH and pH-free-fall conditions was determined during glucose metabolism by resting cells. Anaerobic glycolysis was inhibited more strongly by fluoride than was aerobic glycolysis. Intracellular levels of 3-phosphoglyceric, 2-phosphoglyceric, and phosphoenolpyruvic acids were lower under anaerobic conditions than under aerobic conditions. Thus, S. sanguis had a low phosphoenolpyruvate (PEP) potential under anaerobic conditions. This low PEP potential was suggested to account for the more effective fluoride inhibition of enolase and, consequently, the reduced transport of sugar by the PEP-dependent phosphotransferase system of this micro-organism.