Liu Ya-ling, Hu Tao, Zhang Jing-yi, Zhou Xue-dong
Key Laboratory of Oral Biochemical Engineering, Ministry of Education, Sichuan University, Chengdu, China.
Shanghai Kou Qiang Yi Xue. 2005 Dec;14(6):605-7.
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.
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.
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.
In the dental plaque biofilm, A. naeslundii could ureolyze highly actively; ureolysis could moderate the pH balance of plaque significantly.
初步探讨内氏放线菌的尿素分解作用在天然牙菌斑生物膜中能否保持高水平，以及尿素分解作用对菌斑环境pH平衡的影响。
采用酶动力学试验检测尿素分解的最佳条件；产酸后测量尿素分解过程中的pH变化。使用SPSS软件包进行线性回归和相关性分析。
脲酶的米氏常数为7.5mmol/L，在口腔中常见的尿素浓度范围为3 - 10mmol/L时，其可保持20%至63%的最佳活性；尿素分解的最佳pH值为6.5，但在牙菌斑的临界pH值5.0时，该酶具有40%的最佳活性；在口腔中常见的尿素浓度下，酸化后尿素分解不会使pH值降至临界pH值。
在牙菌斑生物膜中，内氏放线菌可高度活跃地进行尿素分解；尿素分解可显著调节菌斑的pH平衡。
