Discovery of antimicrobial compounds targeting bacterial type FAD synthetases

María Sebastián,Ernesto Anoz-Carbonell,Begoña Gracia,Pilar Cossio,José Antonio Aínsa,Isaías Lans,Milagros Medina

doi:10.1080/14756366.2017.1411910

Abstract

The increase of bacterial strains resistant to most of the available antibiotics shows a need to explore novel antibacterial targets to discover antimicrobial drugs. Bifunctional bacterial FAD synthetases (FADSs) synthesise the flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD). These cofactors act in vital processes as part of flavoproteins, making FADS an essential enzyme. Bacterial FADSs are potential antibacterial targets because of differences to mammalian enzymes, particularly at the FAD producing site. We have optimised an activity-based high throughput screening assay targeting Corynebacterium ammoniagenes FADS (CaFADS) that identifies inhibitors of its different activities. We selected the three best high-performing inhibitors of the FMN:adenylyltransferase activity (FMNAT) and studied their inhibition mechanisms and binding properties. The specificity of the CaFADS hits was evaluated by studying also their effect on the Streptococcus pneumoniae FADS activities, envisaging differences that can be used to discover species-specific antibacterial drugs. The antimicrobial effect of these compounds was also evaluated on C. ammoniagenes, S. pneumoniae, and Mycobacterium tuberculosis cultures, finding hits with favourable antimicrobial properties.

Highlights

An important innovation gap in the discovering of antibiotics has occurred during the last two decades[1], with only five new classes available and 51 new antimicrobials in clinical development[2,3,4]
Considering the structural similarity among Corynebacterium ammoniagenes FADS (CaFADS) and the flavin adenine dinucleotide (FAD) synthetases (FADSs) from the human pathogens Streptococcus pneumoniae and Mycobacterium tuberculosis, we explored the potential antimicrobial effect of the FADS highthroughput screening (HTS) hits in these microorganisms by determining their minimal inhibitory concentration (MIC)
Effect of the HTS hits on the RFK and FMN:adenylyltransferase activity (FMNAT) activities of CaFADS

Summary

Introduction

An important innovation gap in the discovering of antibiotics has occurred during the last two decades[1], with only five new classes available and 51 new antimicrobials in clinical development[2,3,4]. The selection of multi-drug resistant microorganisms[5] encourages to search for new antimicrobial drugs capable of inhibiting novel protein targets, such as those controlling the biosynthesis of essential biomolecules. All living organisms contain a great number of such proteins and many of them are involved in essential functions[6,7,8], including protein folding[9], electron transport in the respiratory and photosynthetic chains[10], b-oxidation of fatty acids[11], nucleotide synthesis or signal transduction[12], among others. Low levels, of FMN and FAD lead to the accumulation of apoflavoproteins, unable to perform the flavin-dependent functions, resulting in the concomitant death of the cell or the organism[13,14].

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Results

Discussion

Conclusion