The Diverse Binding Modes Explain the Nanomolar Levels of Inhibitory Activities Against 1-Deoxy-d-Xylulose 5-Phosphate Reductoisomerase from Plasmodium falciparum Exhibited by Reverse Hydroxamate Analogs of Fosmidomycin with Varying N-Substituents

It is established that reverse hydroxamate analogs of fosmidomycin inhibit the growth of <i>Plasmodium falciparum</i> by inhibiting 1-deoxy-d-xylulose 5-phosphate reductoisomerase (DXR), the second enzyme of the non-mevalonate pathway, which is absent in humans. Recent biochemical studies have demonstrated that novel reverse fosmidomycin analogs with phenylalkyl substituents at the hydroxamate nitrogen exhibit inhibitory activities against <i>Pf</i>DXR at the nanomolar level. Moreover, crystallographic analyses have revealed that the phenyl moiety of the <i>N</i>-phenylpropyl substituent is accommodated in a previously unidentified subpocket within the active site of <i>Pf</i>DXR. In this study, the crystal structures of <i>Pf</i>DXR in complex with a series of reverse <i>N</i>-phenylalkyl derivatives of fosmidomycin were determined to ascertain whether the high inhibitory activities of the derivatives are consistently attributable to the utilization of the subpocket of <i>Pf</i>DXR. While all reverse fosmidomycin derivatives with an <i>N</i>-substituted phenylalkyl group exhibit potent inhibitory activity against <i>Pf</i>DXR, the present crystal structure analyses revealed that their binding modes to the <i>Pf</i>DXR are not uniform. In these compounds, the nanomolar inhibitory activities appear to be driven by binding modes distinct from that observed for the inhibitor containing the <i>N</i>-phenylpropyl group. The structural information obtained in this study will provide a basis for further design of fosmidomycin derivatives.