镧离子对碱性磷酸酶的作用

Effects of lanthanum on alkaline phosphatase

目的 :研究La3+对肝型及肠型碱性磷酸酶活性的影响及作用机制。方法 :采用磷酸苯二钠法测定酶活性 ,荧光滴定监测La3+对碱性磷酸酶内源性荧光的影响 ,由荧光淬灭方程计算La3+在酶分子上的结合数目及结合常数。结果 :La3+可以增强肝型碱性磷酸酶的活性 ,而对肠型碱性磷酸酶有抑制作用。La3+对两种酶反应的动力学参数有不同的影响。发现La3+对肠型碱性磷酸酶的内源性荧光具有淬灭作用 ,说明La3+的结合可以改变酶分子在溶液中的构象。由荧光淬灭方程 ,测得La3+与肠型碱性磷酸酶只有一类 ,约 78个结合位点 ,结合常数为2 .1× 10 4。结论 :La3+对两种碱性磷酸酶具有不同的作用 ;

Objective: 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. Methods: A traditional colorimetric method was used to measure the activity of AP. The influence of La 3+ on the intrinsic fluorescence of protein was studied by the method of fluorescence titration into the AP solution by LaCl 3. The quenching equation was fitted based on the fluorescence spectrum, and then the binding number and the binding constants were calculated. Results: Lanthanum increasesd the activity of rat liver AP, whereas it decreased that of bovine intestine AP. It was observed that the binding of La 3+ quenched the fluorescence of bovine intestine AP, which indicated that La 3+ 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 2.1×10 4 respectively. Conclusion: La 3+ has different effects on the activities of rat liver AP and bovine intestine AP; the binding of La 3+ can induce the changes of conformation of bovine intestine AP, and inhibit its activity.