IspH metalloenzyme, as a source for the discovery of novel antimicrobials

L'un des moyens de lutter contre la résistance aux antimicrobiens est de se concentrer sur des séries d'enzymes cibles sous-exploitées. Dans la plupart des bactéries et certains parasites, les précurseurs isoprénoïdes sont synthétisés par la voie du 2C-méthyl-d-érythritol 4-phosphate (MEP), absente chez l'homme, et qui représente donc une cible intéressante pour le développement de nouveaux anti-infectieux. IspH est une oxydoréductase contenant un cluster [4Fe-4S]2+ sensible à l'oxygène qui catalyse la dernière étape de la voie du MEP en convertissant l’HMBPP en IPP et DMAPP. Une stratégie pluridisciplinaire a été appliquée pour découvrir de nouvelles classes d'inhibiteurs contre l'IspH de Pseudomonas aeruginosa, Mycobacterium tuberculosis et Plasmodium falciparum. Une méthode a été mise au point pour produire les différents orthologues de l'IspH sous forme d'holoenzymes, suivie par le développement d'un test enzymatique qui a été utilisé pour un criblage in vitro de différentes chimiothèques. Cette dernière a conduit à la découverte d'un puissant nouvel inhibiteur ciblant les trois orthologues. En outre, une approche de prodrogue a été exploitée pour un inhibiteur d'IspH d'E. coli déjà connu ((E)-4-amino-3-méthylbut-2-en-1-yl diphosphate) dans le but d'obtenir une activité antibactérienne, antituberculeuse et antipaludéenne.One way to tackle the arising antimicrobial resistance is to focus on underexploited series of target enzymes. In most bacteria and some parasites, the isoprenoid precursors are synthesized via the 2C-methyl-d-erythritol 4-phosphate (MEP) pathway, which is absent in humans, and it thus represents an interesting target for the development of novel anti-infectives. IspH is an oxidoreductase containing an oxygen-sensitive [4Fe-4S]2+ cluster that catalyzes the last step of the MEP pathway converting HMBPP into IPP and DMAPP. A multidisciplinary strategy has been applied for the discovery of new classes of inhibitors against IspH from Pseudomonas aeruginosa, Mycobacterium tuberculosis and Plasmodium falciparum. A method was developed to produce the IspH orthologs as holoenzymes, followed by the development of the enzymatic assay which was used for an in vitro screening campaign of different chemical libraries. The latter led to the discovery of a novel potent inhibitor targeting the three orthologs object of this study. Moreover, a prodrug approach has been exploited for an already known E. coli IspH inhibitor ((E)-4-amino-3-methylbut-2-en-1-yl diphosphate) with the goal of reaching antibacterial, antitubercular, and antimalarial activity

The Reductive Dehydroxylation Catalyzed by IspH, a Source of Inspiration for the Development of Novel Anti-Infectives

International audienceThe non-mevalonate or also called MEP pathway is an essential route for the biosynthesis of isoprenoid precursors in most bacteria and in microorganisms belonging to the Apicomplexa phylum, such as the parasite responsible for malaria. The absence of this pathway in mammalians makes it an interesting target for the discovery of novel anti-infectives. As last enzyme of this pathway, IspH is an oxygen sensitive [4Fe-4S] metalloenzyme that catalyzes 2H+/2e- reductions and a water elimination by involving non-conventional bioinorganic and bioorganometallic intermediates. After a detailed description of the discovery of the [4Fe-4S] cluster of IspH, this review focuses on the IspH mechanism discussing the results that have been obtained in the last decades using an approach combining chemistry, enzymology, crystallography, spectroscopies, and docking calculations. Considering the interesting druggability of this enzyme, a section about the inhibitors of IspH discovered up to now is reported as well. The presented results constitute a useful and rational help to inaugurate the design and development of new potential chemotherapeutics against pathogenic organisms

Synthesis and kinetic evaluation of analogs of (E)-4-amino-3-methylbut-2-en-1-yl diphosphate, a potent inhibitor of the IspH metalloenzyme

International audienceOur previous research revealed that (E)-4-amino-3-methylbut-2-en-1-yl diphosphate (AMBPP) is one of the best inhibitors of IspH, a [4Fe-4S]-dependent enzyme involved in the methylerythritol phosphate pathway that is a valuable target for the discovery of new antibacterial and antiparasitic drugs as it is absent in humans. AMBPP has substantial limitations for drug development due to its poor metabolic stability. Here, we investigate the replacement of the diphosphate moiety of AMBPP by more stable mimics: sulfonate, phosphonate or phosphinophosphonate. After synthesis of the derivatives, enzymatic assays demonstrated that none of these AMBPP analogs is an efficient IspH inhibitor