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Table 2 Effect of metal ions and EDTA on Nk activity

From: Cloning and enhancing production of a detergent- and organic-solvent-resistant nattokinase from Bacillus subtilis VTCC-DVN-12-01 by using an eight-protease-gene-deficient Bacillus subtilis WB800

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

  1. 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-p NA as a substrate at pH 9 and 65°C.