The iron-sulfur cluster in the L-serine dehydratase TdcG from Escherichia coli is required for enzyme activity

The anaerobically inducible L-serine dehydratase, TdcG, from Escherichia coli was characterized. Based on UV-visible spectroscopy, iron and labile sulfide analyses, the homodimeric enzyme is proposed to have two oxygen-labile [4Fe-4S](2+) clusters. Anaerobically isolated dimeric TdcG had a k(cat) of 544 s(-1) and an apparent K-M for L-serine of 4.8 mM. L-threonine did not act as a substrate for the enzyme. Exposure of the active enzyme to air resulted in disappearance of the broad absorption band at 400-420 nm, indicating a loss of the [4Fe-4S](2+) cluster. A concomitant loss of dehydratase activity was demonstrated, indicating that integrity of the [4Fe-4S](2+) cluster is essential for enzyme activity. (C) 2004 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.