INHIBITION OF PURIFIED ENOLASES FROM ORAL BACTERIA BY FLUORIDE

Enolase activity in strains of oral streptococci previously has been f ound to be inhibited by 50% (K-i) by fluoride concentrations ranging f rom 50 to 300 mu M or more in the presence of 0.5 to 1.0 mM inorganic phosphate ions. In this study, enolase was extracted and partly purifi ed by a two-step process from five oral bacterial species and the effe ct of fluoride on the kinetics of enolase examined. The molecular weig ht of the putative enolase proteins was 46-48 kDa. The V-max values ra nged from 20 to 323 IU/mg and K-m for glycerate-2-phosphate from 0.22 to 0.74 mM. Enolase activity was inhibited competitively by fluoride, with K-i values ranging from 16 to 54 mu M in the presence of 5 mM ino rganic phosphate ions. K-i values for phosphate ranged from 2 to 8 mM. The enolase from Streptococcus sanguis ATCC 10556 was more sensitive to fluoride (K-i=16+/-2) than was enolase from Streptococcus salivariu s ATCC 10575 (K-i=19+/-2) or Streptococcus mutans NCTC 10449 (K-i=40+/ -4) and all three streptococcal strains were more sensitive to fluorid e than either Actinomyces naeslundii WW 627 (K-i=46+/-6) or Lactobacil lus rhamnosus ATCC 7469 (K-i=54+/-6) enolases. The levels of fluoride found to inhibit the streptococcal enolases in this study are much low er than previously reported and are likely to be present in plaque, es pecially during acidogenesis, and could exert an anti-glycolytic effec t.