Thermodynamic Investigation of Inhibitor Binding to 1-Deoxy-d-Xylulose-5-Phosphate Reductoisomerase

d-xylulose-5-phosphatereductoisomerase (DXR), a target for developing novel anti-infectives.The binding of hydroxamate inhibitors to Escherichia coli DXR is Mg²⁺-dependent, highly endothermic (ΔH, 22.7–24.3 kJ/mol), and entropy-driven, while thatof nonhydroxamate compounds is metal ion-independent and exothermic(ΔH, −19.4 to −13.8 kJ/mol),showing that hydration/dehydration of the enzyme metal ion bindingpocket account for the drastic ΔH change. However,for DXRs from Plasmodium falciparum and Mycobacteriumtuberculosis, the binding of all inhibitors is exothermic(ΔH, −24.9 to −9.2 kJ/mol), suggestingthat the metal ion binding sites of these two enzymes are considerablyless hydrated. The dissociation constants measured by ITC are wellcorrelated with those obtained by enzyme inhibition assays (R² = 0.75). Given the rapid rise of antibioticresistance, this work is of interest since it provides novel structuralimplications for rational development of potent DXR inhibitors.