Phosphoenolpyruvate‐dependent glucose phosphotransferase activity in Streptococcus mitis ATCC 903

Abstract

– A constitutive phosphoenolpyruvate (PEP)‐dependent glucose phosphotransferase system was found in decryptified cells of Strep. mitis. The system displayed saturation kinetics and the apparent Km value for the non‐fermentable analogue 2‐deoxyglucose (2DG) was 0.4 mm. Sodium fluoride inhibited the activity when 2‐phosphoglycerate was used as the energy source instead of PEP, Intact cells accumulated 2DG and also a derivative that behaved chromatographically like 2DG‐6‐phosphate. PEP‐dependent glucose phosphotransferase activity was also demonstrated in freshly collected plaque.

Glucose Incorporation by Human Dental Plaque Bacteria

“…Further experiments using pure oral bacteri al strains and subcellular vesicles prepared from these bacteria are necessary to deter mine the precise sugar transport mecha nisms present. Glucose transport occurs by PEP-dependent PTS systems when these bacteria are present as a mixed collection as found in dental plaque [Roberts and Linder, 1980], and the present work shows that in corporation also occurs by other mecha nisms.…”

“…3). 2-Deoxyglucose is non-utilisable by S. mitis and 5. mutans and accu mulates in the cell as the free sugar and as 2-deoxyglucose-6-phosphate [Schachtele and Leung, 1975;Roberts and Linder, 1980]. The saturating part of the 2-deoxyglucose curve may represent an inhibition of uptake due to a build-up of these compounds inside the cell or it may reflect a dynamic equilib rium between uptake and exit reactions.…”

“…Exponential phase cells of S. mitis ATCC 903 were obtained as described previously [Roberts and Linder, 1980]. The cells were grown at 37 °C in screw-capped bottles containing standard pro teose-peptone medium and 28 mM glucose and then suspended by homogenisation in ice-cold 50 mM sodium phosphate buffer (pH 6.8) con taining 10 mM magnesium sulphate (MP buffer).…”

“…The inhibition studies indicate that glucose transport mechanisms other than phosphoenolpyruvate-dependent phosphotransferase systems are also present in oral bacteria. [Kanapka and Hamil ton, 1971;Schachtele and Mayo, 1973;Roberts and Linder, 1980] and sucrose PTS systems have been reported for S. sanguis [Mayo et al, 1978] and 5. mutans [Slee and Tanzer, 1979;St. Martin and Wittenberger, 1979].…”

Effect of Orthophosphates and Citrates in Fluoride Toothpastes on Plaque pH (Short Communication)

“…Since that time many at tempts have been made to measure the acidity of den tal plaque following the consumption of sugar or other carbohydrate products, either measuring in vitro [Stephan, 1940[Stephan, , 1944Frostell, 1969;Geddes, 1975] or telemetrically in situ [Graf, 1970;Imfield, 1972;Mortimer et al, 1984], Fluoride has been shown to inhibit acid produc tion in dental plaque [Jenkins, 1959;Geddes and McNee, 1982;Van der Hoeven and Franken, 1984] and has also been shown to inhibit the glycolytic en zyme enolase [Stone and Werkman, 1937], Because of this, fluoride inhibits the glucose uptake into the cell via the phosphoenolpyruvate/phosphotransferase system [Hamilton, 1977;Roberts and Linder, 1980]. In the present study other known glycolytic inhibitors were evaluated for their effect on postchallenge plaque pH.…”