Biochemical properties of M. tuberculosis IspE. a. The optimal pH for catalytic activity was determined using MES (pH 5.5 - pH 7.0), MOPS (pH 7.0 - pH 7.5), Tris (pH 7.5 - pH 8.5), TAPS (pH 8.5 - pH 9.0), and CAPS (pH 9.0 - pH 10.5) using appropriate counter ions. b. Divalent cations (Mg2+, Mn2+, Zn2+, or Ca2+) were added to the reaction mixtures at the indicated concentrations. The reaction mixtures were as described in Experimental Procedures.