[Effect of metal ions on the glucose isomerase activity of Streptomyces robeus S-606].

The intracellular glucose isomerase produced by Str. robeus S-606 refers to the group of isomerases activated most effectively by Mg2+. Besides, an activating effect of Fe3+, Co2+ and Mn2+ is observed. The optimal Mg2+ concentration for the D-glucose isomerization to D-fructose is 10(-2) M, and that of Co2+ is 100 times as low. Addition of Ca2+ (above 10% of the Mg2+ content) to the reaction mixture with the optimal Mg concentration inhibits the enzyme. At the same time Co2+ increases thermostability of glucose isomerase to a greater extent than Mg2+.