Differences in Acidogenicity of <i>S. sobrinus</i> and <i>S. rattus</i> Are Linked to the Catalytic Efficiency of the Glycolytic Key Enzyme Phosphofructokinase

Abstract

This contribution describes the biochemical properties of two catalytically different phosphofructokinases (PFKs) purified from Streptococcus rattus LB 2 (PFK–rat) and Streptococcus sobrinus OMZ 65 (PFK–sob), respectively. Steady–state kinetics revealed K_M = 0.8 mM for PFK–rat and K_M = 0.08 mM for PFK–sob for F–6–P as the substrate. The enzymes also differ in their pH profiles: whereas the highest activity of PFK–rat was measured at pH = 8.0, the optimum pH of PFK–sob was at pH = 7.0. In addition, compared to PFK–sob, PFK–rat was more sensitive against the allosteric inhibitor ATP. PFK catalyzes a committed step of glycolysis, the main acid producing catabolic pathway. Thus, the catalytically more efficient enzyme isolated from S. sobrinus OMZ 65, especially at low pH, could explain the comparably high acidogenicity of this strain.

Phylogenetic Analyses of the Water-Insoluble Glucan Synthesizing Glucosyltransferase Gene of Streptococcus ratti

“…S. ratti strain FA-1 (GTC 00245 ), which was isolated from rats by Fitzgerald (13); strain BHT, which was isolated from humans by Zinner (14); strain LB-2, which was isolated from humans by Gansser (15); and S. salivarius ATCC 25975 were used in this study. The strains were grown for 24 hours at 37°C under anaerobic conditions on Bact Brain Heart Infusion (BHI ; Becton, Dickinson, and Company NJ, USA)agar.…”