3. Results and discussion

3.1 Effects of metal ions

Several divalent metal ions (Ca2+, Mn2+, Zn2+, Mg2+, Ni2+, Cu2+ and Ba2+) were selected to investigate the effect of metal ions on DAADH activity (Fig.2a). Ni2+ activated DAADH by 128.3%. Ca2+, Ba2+, Mg2+ inhibit the activity of DAADH. The effect of Ni2+ concentrations on enzyme activity was studied as shown (Fig.2b). Maximum enzyme activity was obtained with 15 mM Ni2+, which was 161.2% of the initial activity .