FadD32 has been identified as one of the most vulnerable and promising enzyme targets for antitubercular therapeutic development. This essential enzyme catalyzes the penultimate step in mycolic acid biosynthesis and inhibition is lethal for Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB). We report herein two approaches for the identification of FadD32 inhibitors. In the first approach we designed and synthesized a bisubstrate inhibitor that mimics the acyl-adenylate intermediate (formed by condensation of the meromycolic acid and ATP) through replacement of the labile phosphate linkage with a sulfamate isostere. Systematic optimization of the acyl chain through truncation led to 11-phenoxyundecanoyl adenosine monosulfamate (PhU-AMS) with good enzyme selectivity as well as fairly potent whole-cell activity. This compound served as a useful chemical probe and positive control for our subsequent screen. To identify other chemotypes we then developed a medium throughput gel-based assay that directly reports on FadD32 catalyzed loading of a fluorescent fatty acid onto full-length Pks13. Using this functional assay, we screened the publically available GlaxoSmithKline antimycobacterial compound set. We will report the results of both of our synthetic and screening efforts and include key biochemical, structural, and microbiological support for their mechanism of action.

Identification of whole-cell active inhibitors of Mycobacterium tuberculosis FadD32

251st National Meeting (2016)

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