IspG enzyme activity in the deoxyxylulose phosphate pathway: roles of the iron-sulfur cluster.

IspG is a [4Fe-4S] cluster-containing protein, and the 4Fe-4S species is proposed to be the catalytically relevant species. However, attempts reported in the literature failed to detect the 4Fe-4S species. In this study, using a potent reduction system, we have successfully detected the 4Fe-4S species with X-band EPR spectroscopy. In addition, we have improved the Escherichia coli IspG activity to 550 nmol min(-1) mg(-1), which is approximately 20-fold greater than that of the NADPH-Fpr-FldA system in the literature.