The optimal pH values of recombinant SdIDH were a broad range of 8.5–9.5 with Mg2+ and of 8.0–10.0 with Mn2+, similar with those of homodimeric IDHs from E. coli (pH 7.5–10.0) and Helicobacter pylori (around pH 9.0), as well as other monomeric IDHs from Desulfobacter vibrioformis (pH 8.0–9.0) and C. glutamicum (pH 7.5–10).