Figure 5.

Divalent cation requirement for the 400K enzyme. The 400K enzyme was dialyzed for 2 h in 2 L of 2 mm EDTA and 2 mm EGTA to remove endogenous cations, and then dialyzed twice in 2 L of 20 mm Tes, pH 7.5, and 0.5 mm DTT to remove the chelators. Enzyme was added to an assay vessel that contained divalent cations and necessary components. Rates are expressed as relative percentages of the maximum rate (0.093 μmol min⁻¹ mg⁻¹).