A better understanding of leishmaniasis was provided when French et al. demonstrated that L. donovani uridine 5′-monophosphate synthase (LdUMPS) is an essential enzyme for promastigotes viability and presented the crystal structure of the LdUMPS in complex with its product, UMP35.Their structural analysis revealed a tetrameric structure for LdUMPD with two dimeric OMPDC and two dimeric OPRT functional domains. The gene discussed is UMPS; the disease is leishmaniasis.