<p> The conversion of dTDP-glucose into dTDP-4-keto-6-deoxyglucose by <taxon tax_id="562">Escherichia coli</taxon> dTDP-glucose 4,6-dehydratase) takes place in the active site in three steps: dehydrogenation to dTDP-4-ketoglucose, dehydration to dTDP-4-ketoglucose-5,6-ene, and rereduction of C6 to the methyl group. The 4,6-dehydratase makes use of tightly bound NAD<sup>+</sup> as the coenzyme for transiently oxidizing the substrate, activating it for the dehydration step [<cite idref="PUB00007907"/>]. This and other 4,6-dehydratases catalyze the first committed step in all 6-deoxysugar biosynthetic pathways described to date. Numerous6-deoxysugars are used in bacterial lipopolysaccharide production as well as in the biosynthesis of a diverse array of secondary metabolites.</p>