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. 2013 Sep 10;12:79. doi: 10.1186/1475-2859-12-79

Table 2.

Effect of metal ions and EDTA on Nk activity

Additive Remaining activity (%) at concentration (mM) of
1 5 10
Ca2+
 82 ± 6.71
 91 ± 2.94
 105 ± 5.46
Cu2+
 85 ± 1.68
 85 ± 3.78
 74 ± 2.52
Fe2+
 101 ± 3.36
 103 ± 0.42
 104 ± 3.78
Mg2+
 141 ± 1.68
 162 ± 2.10
 124 ± 14.69
Mn2+
 85 ± 1.26
 98 ± 2.10
 110 ± 5.46
Ni2+
 91 ± 11.33
 105 ± 3.36
 105 ± 3.78
Zn2+
 73 ± 10.91
 75 ± 8.39
 107 ± 2.52
EDTA 118 ± 6.71 22 ± 0.42 21 ± 0.00

0.6 μg of Nk was incubated in 50 mM Na-phosphate buffer pH 8 at 30°C for 1 h in the presence of 1, 5 or 10 mM of different metal ions. The Nk activity was measured with 1 mM Suc-AAPF-pNA as a substrate at pH 9 and 65°C.