Hu Jian, Jia Yu, Liu Xiang-Tao, Li Rong-Chang, Wang Kui
Department of Chemical Biology, Peking University School of Pharmaceutical Sciences, Beijing 100083, China.
Beijing Da Xue Xue Bao Yi Xue Ban. 2003 Apr 18;35(2):176-9.
To investigate the effects of lanthanum on the activities of two kinds of alkaline phosphatase (AP)-rat liver AP and bovine intestine AP, and the preliminary mechanism involved.
A traditional colorimetric method was used to measure the activity of AP. The influence of La3+ on the intrinsic fluorescence of protein was studied by the method of fluorescence titration into the AP solution by LaCl3. The quenching equation was fitted based on the fluorescence spectrum, and then the binding number and the binding constants were calculated.
Lanthanum increased the activity of rat liver AP, whereas it decreased that of bovine intestine AP. It was observed that the binding of La3+ quenched the fluorescence of bovine intestine AP, which indicated that La3+ could change the conformation of AP in solution. The number of binding sites and the binding constants that were calculated based on the fitted quenching equation were 78 and 2.1 x 10(4) respectively.
La3+ has different effects on the activities of rat liver AP and bovine intestine AP; the binding of La3+ can induce the changes of conformation of bovine intestine AP, and inhibit its activity.
研究镧对两种碱性磷酸酶（AP）——大鼠肝脏碱性磷酸酶和牛小肠碱性磷酸酶活性的影响及其初步作用机制。
采用传统比色法测定碱性磷酸酶活性。通过向碱性磷酸酶溶液中滴加氯化镧的荧光滴定法研究La3+对蛋白质固有荧光的影响。基于荧光光谱拟合猝灭方程，进而计算结合数和结合常数。
镧可提高大鼠肝脏碱性磷酸酶的活性，而降低牛小肠碱性磷酸酶的活性。观察到La3+的结合使牛小肠碱性磷酸酶的荧光猝灭，这表明La3+可改变溶液中碱性磷酸酶的构象。根据拟合的猝灭方程计算出的结合位点数和结合常数分别为78和2.1×10(4)。
La3+对大鼠肝脏碱性磷酸酶和牛小肠碱性磷酸酶的活性有不同影响；La3+的结合可诱导牛小肠碱性磷酸酶构象改变并抑制其活性。
