Effects of metal ions on enzyme activity. The purified BL-αGTase activity was measured under standard conditions (pH 6.0 at 40 °C) with amylose and G2 as donor and acceptor in the presence of 5 mM Ca2+, Mg2+, Cu2+, Mn2+, Co2+, Zn2+, Fe2+, or EDTA. Bars with different letters are significantly different at p < 0.05 in Duncan’s multiple range test