6-phosphogluconate dehydratase from Zymomonas mobilis: an iron-sulfur-manganese enzyme.

The enzyme 6-phosphogluconate dehydratase has been isolated in a stable form by a simple one-step procedure using dye ligand chromatography. The role of metal ions in the activity and stability of the enzyme was investigated. As with aconitase and several other dehydratase enzymes, the active site includes an Fe4S4 cluster. In addition, the purified enzyme has been shown to contain one manganese ion per subunit, which is also essential for activity. Rapid inactivation by superoxide radical was observed, which could only partly be protected by manganous ions The purified enzyme could be stabilised by alpha-glycerophosphate in place of manganese; glycerophosphate mimics the carbon atoms 4 to 6 of the natural substrate. This suggests that the manganous ion may involved in binding this part of the substrate.