牛小肠碱性磷酸酶分子不对称性的研究

目的通过2个化学同一性亚基构成的二聚体牛小肠碱性磷酸酶(CIP酶)亚基间的相互作用,探讨酶分子的不对称性。方法采用热失活法研究不同温度条件下,CIP活力变化,并与EDTA脱锌失活以及加锌复活后的动力学参数进行比较。结果CIP的热失活是一个两相动力学过程,且初始1/2(快相)的活力比其余1/2(慢相)的活力遭破坏要快。温度的改变对慢相速率常数的影响比快相明显。EDTA致酶失活也表现为两相动力学过程。apo酶复活的动力学过程同样表明,锌离子与结合位点的再结合也是分部位按顺序进行的。结论CIP 2个化学同一性的亚基非功能同一,在溶液中酶分子并不具有真正的C2系统,CIP酶分子具有不对称性。

Molecule Asymmetry in Alkaline Phosphatase of Calf Intestine

Objective The dimeric CIPis known to be made up of chemically identical monomer.It is still a problem that CIPmolecule is asymmetry or not.Methods The present experiment investigated changes of thermal inactivation of CIPat different temperatures.Data have been compared with that of inactivation of this enzyme with EDTAand its subsequent reactivation with Zn²⁺ ions.Results The results showed that the kinetic behavior was a biphase process involving fast and slow phases of thermal inactivation.Half of the initial activity was destroyed much more rapidly than the remaining half.At EDTAconcentration 1～5 mmol/L, the inactivation processes were two-phases.This peculiar kinetic behavior was an inherent property of the enzyme protein and was not acquired by its interaction with some ligand under any specific condition.Conclusion The biphasic process of thermal inactivation and EDTAcausing inactivation indicate that the two subunits of CIPare functionally not identical and the enzyme is asymmetry in molecule.