Abstract: 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.

Key words: alkaline phosphatase, thermal inactivation, EDTA, Zn²⁺