6-PHOSPHOGLUCONATE DEHYDRATASE FROM ZYMOMONAS-MOBILIS - AN IRON-SULFUR-MANGANESE ENZYME

The enzyme 6-phosphogluconate dehydratase has been isolated in a stabl e form by a simple one-step procedure using dye ligand chromatography. The role of metal ions in the activity and stability of the enzyme wa s investigated. As with aconitase and several other dehydratase enzyme s, the active site includes an Fe4S4 cluster. In addition, the purifie d enzyme has been shown to contain one manganese ion per subunit, whic h is also essential for activity. Rapid inactivation by superoxide rad ical was observed, which could only partly be protected by manganous i ons 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 in volved in binding this part of the substrate.