Disagree with the results of Zhou et al. [21], soil enzyme activity was found to be a different degree of
recovery after a long period of heavy metals stress in their research, which would be contributed to the
different concentrations of heavy metals. The inhibition effect of heavy metals to soil enzyme activities
was the results of the changes of chemical conformation mainly due to the coordination reaction. Based
on lewis's hard and soft acids and base theory (HSAB), the active sites in enzyme protein molecular,
such as thiol or imidazolyl groups, were preferred coordinated with soft heavy metals.