title: [A preliminary study of the modulation of Actinomyces naeslundii urease to the pH balance of dental biofilm].
abstract: OBJECTIVE
  To explore whether the ureolysis of Actinomyces naeslundii could keep high level in the natural dental biofilm and the effect of ureolysis on the environmental pH balance preliminarily.
  
  
  METHODS
  Enzyme kinetic test was used to detect the optimal condition for ureolysis; and the pH change was measured under ureolysis after acidgenesis.SPSS software package was used for linear regression and correlation analysis.
  
  
  RESULTS
  The Km of urease was 7.5mmol/L, it could keep 20% to 63% of the optimal activity with the concentration of urea normally found in the mouth which was at the range of 3-10mmol/L; The optimal pH of ureolysis was 6.5, but at pH 5.0 which was the threshold pH of dental plaque, the enzyme had 40% of the optimal activity; with the concentration of urea normally found in the mouth, pH would not decrease to the threshold pH with ureolysis after acidification.
  
  
  CONCLUSIONS
  In the dental plaque biofilm, A. naeslundii could ureolyze highly actively; ureolysis could moderate the pH balance of plaque significantly.
authors.affiliation: Key Laboratory of Oral Biochemical Engineering, Ministry of Education, Sichuan University, Chengdu, China.
authors.forename: Ya-ling
authors.initials: YL
authors.lastname: Liu
authors.forename: Tao
authors.initials: T
authors.lastname: Hu
authors.forename: Jing-yi
authors.initials: JY
authors.lastname: Zhang
authors.forename: Xue-dong
authors.initials: XD
authors.lastname: Zhou
mesh_terms: D000190:Actinomyces / Q000201:enzymology*; D018441:Biofilms; D003773:Dental Plaque / Q000382:microbiology*; D006863:Hydrogen-Ion Concentration; D014510:Urease / Q000378:metabolism*
chemical_list: D014510:Urease