1-deoxy-D-xylulose 5-phosphate reductoisomerase (DXR) as target for anti Toxoplasma gondii agents: crystal structure, biochemical characterisation and biological evaluation of inhibitors.

Abstract

Toxoplasma gondii is a widely distributed apicomplexan parasite causing toxoplasmosis, a critical health issue for immunocompromised individuals and for congenitally infected foetuses. Current treatment options are limited in number and associated with severe side effects. Thus, novel anti-toxoplasma agents need to be identified and developed. 1-deoxy-D-xylulose 5-phosphate reductoisomerase (DXR) is considered the rate-limiting enzyme in the non-mevalonate pathway for the biosynthesis of the isoprenoid precursors isopentenyl pyrophosphate (IPP) and dimethylallyl diphosphate (DMAPP) in the parasite, and has been previously investigated for its key role as a novel drug target in some species, encompassing Plasmodia, Mycobacteria and E. coli. In this study, we present the first crystal structure of T. gondii DXR (TgDXR) in a tertiary complex with the inhibitor fosmidomycin and the cofactor NADPH in dimeric conformation at 2.5 Å resolution revealing the inhibitor binding mode. In addition, we biologically characterize α-phenyl-ß-thia and -oxa reverse fosmidomycin analogues and show that some derivatives are strong inhibitors of TgDXR which also, in contrast to fosmidomycin, inhibit the growth of T. gondii in vitro. Here, ((3,4-dichlorophenyl)((2-(hydroxy(methyl)amino)-2-oxoethyl)thio)methyl)phosphonic acid was identified as the most potent anti T. gondii compound. These findings will enable the future design and development of more potent anti-toxoplasma DXR inhibitors.