Isolation, characterization, and inhibition kinetics of enolase from Streptococcus rattus FA-1.

One aspect in a broad spectrum of possible mechanisms of cariostatic reactions of fluoride is its interaction with the metabolism of oral bacteria. Information on the mechanisms and kinetics of fluoride inhibition of essential enzymes of the glycolytic pathway of the relevant bacteria is lacking. In this work, the isolation and purification of enolase from Streptococcus rattus and its characterization are described. The enzyme has been isolated in a monomeric (22 kilodaltons) and dimeric (49 kilodaltons) form. The Km for 2-phosphoglycerate is 4.35 mM. Fluoride inhibition kinetics have competitive character, while phosphate in concentrations above 2 mM and in the presence of 0.5 mM fluoride alters the inhibition kinetics from competitive to noncompetitive. Without fluoride, 2 mM phosphate has a slight stimulatory effect on the enzyme. Monofluorophosphate has a noncompetitive inhibiting effect on the enzyme. This finding suggests that the effect of phosphate may be due to an additional binding of fluoride to the enolase, resulting in a conformational change of the enzyme.