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The production of itaconate by macrophages was only discovered in 2011. An increasing number of studies have since revealed essential biological functions for this small molecule, ranging from antimicrobial to immunomodulator. The antibacterial role of itaconate has however been questioned because the estimated concentration of itaconate in macrophages (low-millimolar) is lower than the minimum inhibitory concentration (MIC) of itaconate reported for several bacterial strains (low-to-mid-millimolar). We note that some of these investigations have tended to ignore the high acidity of this small diacid (pKas 3.85 and 5.45), thereby potentially biassing activity measurements. We measured the MIC of itaconate in Escherichia coli (not known to metabolize itaconate) and in Salmonella enterica serovar Typhimurium (known to metabolize itaconate) at varying pH values to probe the effect that pH has on itaconate toxicity. Herein, we demonstrate that the antimicrobial effect of itaconate is dependent upon the pH of the media and that itaconate does have antimicrobial activity at biologically relevant pH and concentrations. Under nutrient-poor conditions, the antimicrobial activity of itaconate in both E. coli and S . Typhimurium increased approximately 200-fold when the pH was dropped by one unit, whereas itaconate was not found to be toxic under nutrient rich conditions. Our results also reveal that the activity of itaconate is synergistic with acidity, yet is not a function of increased permeability with protonation. Similar experiments performed with succinate (a pKa-matched diacid) yielded drastically different results, consistent with a target-based mechanism of action for itaconate. Overall, our work shows the importance of controlling the pH when performing experiments with itaconic acid.

Pantothenate kinase (PanK) catalyzes the transformation of pantothenate to 4'-phosphopantothenate, the first committed step in coenzyme A biosynthesis. While numerous pantothenate antimetabolites and PanK inhibitors have been reported for bacterial type I and type II PanKs, only a few weak inhibitors are known for bacterial type III PanK enzymes. Here, a series of pantothenate analogues were synthesized using convenient synthetic methodology. The compounds were exploited as small organic probes to compare the ligand preferences of the three different types of bacterial PanK. Overall, several new inhibitors and substrates were identified for each type of PanK., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Aminoglycosides are a group of broad-spectrum antibiotics that have been used in the clinic for almost a century. The rapid spread of bacterial genes coding for aminoglycoside-modifying enzymes has, however, dramatically decreased the utility of aminoglycosides. We have previously reported several aminoglycoside potentiators that work by inhibiting aminoglycoside N-6'-acetyltransferase, one of the most common determinants of aminoglycoside resistance. Among these, prodrugs that combine the structure of an aminoglycoside with that of pantothenate into one molecule are especially promising. We report here a series of cellular studies to investigate the activity and mechanism of action of these prodrugs further. Our results reveal a new aminoglycoside resistance inhibitor, as well as the possibility that these prodrugs are transformed into more than one inhibitor in bacteria. We also report that the onset of the potentiators is rapid. Their low cell cytotoxicity, good stability, and potentiation of various aminoglycosides, against both Gram-positive and Gram-negative bacteria, make them interesting compounds for the development of new drugs., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

In the context of increasing global antibiotic resistance, the need for alternative therapeutic targets is great. Although new antibiotics and resistance inhibitors provide temporary solutions, they are bound to become obsolete. In this work, we propose a new approach, coined "bacterio-modulation" that aims to restore macrophage potency towards bacterial strains that are able to survive in phagolysosomes. One key defense in the macrophage's arsenal is itaconate, an endogenous molecule with antimicrobial activity. Some intracellular pathogens have evolved to produce itaconate-degrading enzymes, which are required for intracellular proliferation and to promote pathogenicity. We herein present the first molecule able to resensitize Salmonella enterica to itaconate., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Pantothenamides are N-substituted pantothenate derivatives which are known to exert antimicrobial activity through interference with coenzyme A (CoA) biosynthesis or downstream CoA-utilizing proteins. A previous report has shown that replacement of the ProR methyl group of the benchmark N-pentylpantothenamide with an allyl group (R-anti configuration) yielded one of the most potent antibacterial pantothenamides reported so far (MIC of 3.2 μM for both sensitive and resistant Staphylococcus aureus). We describe herein a synthetic route for accessing the corresponding R-syn diastereomer using a key diastereoselective reduction with Baker's yeast, and report on the scope of this reaction for modified systems. Interestingly, whilst the R-anti diastereomer is the only one to show antibacterial activity, the R-syn isomer proved to be significantly more potent against the malaria parasite (IC50 of 2.4±0.2 μM). Our research underlines the striking influence that stereochemistry has on the biological activity of pantothenamides, and may find utility in the study of various CoA-utilizing systems., (Copyright © 2014. Published by Elsevier Ltd.)

The most common mechanism of resistance to aminoglycoside antibiotics entails bacterial expression of drug-metabolizing enzymes, such as the clinically widespread aminoglycoside N-6'-acetyltransferase (AAC(6')). Aminoglycoside-CoA bisubstrates are highly potent AAC(6') inhibitors; however, their inability to penetrate cells precludes in vivo studies. Some truncated bisubstrates are known to cross cell membranes, yet their activities against AAC(6') are in the micromolar range at best. We report here the synthesis and biological activity of aminoglycoside-pantetheine derivatives that, although devoid of AAC(6') inhibitory activity, can potentiate the antibacterial activity of kanamycin A against an aminoglycoside-resistant strain of Enterococcus faecium. Biological studies demonstrate that these molecules are potentially extended to their corresponding full-length bisubstrates by enzymes of the coenzyme A biosynthetic pathway. This work provides a proof-of-concept for the utility of prodrug compounds activated by enzymes of the coenzyme A biosynthetic pathway, to resensitize resistant strains of bacteria to aminoglycoside antibiotics.

As a key precursor of coenzyme A (CoA) biosynthesis, pantothenic acid has proven to be a useful backbone to elaborate probes of this biosynthetic pathway, study CoA-utilizing systems, and design molecules with antimicrobial activity. The increasing prevalence of bacterial strains resistant to one or more antibiotics has prompted a renewed interest for molecules with a novel mode of antibacterial action such as N-substituted pantothenamides. Although numerous derivatives have been reported, most are varied at the terminal N-substituent, and fewer at the β-alanine moiety. Modifications at the pantoyl portion are limited to the addition of an ω-methyl group. We report a synthetic route to N-substituted pantothenamides with various alkyl substituents replacing the geminal dimethyl groups. Our methodology is also applicable to the synthesis of pantothenic acid, pantetheine and CoA derivatives. Here a small library of new N-substituted pantothenamides was synthesized. Most of these compounds display antibacterial activity against sensitive and resistant Staphylococcus aureus. Interestingly, replacement of the ProR methyl with an allyl group yielded a new N-substituted pantothenamide which is amongst the most potent reported so far., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Aminoglycoside antibiotics act by binding to 16S rRNA. Resistance to these antibiotics occurs via drug modifications by enzymes such as aminoglycoside 6'-N-acetyltransferases (AAC(6')s). We report here the regioselective and efficient synthesis of N-6'-acylated aminoglycosides and their use as probes to study AAC(6')-Ii and aminoglycoside-RNA complexes. Our results emphasize the central role of N-6' nucleophilicity for transformation by AAC(6')-Ii and the importance of hydrogen bonding between 6'-NH(2) and 16S rRNA for antibacterial activity.

Lovastatin biosynthesis in Aspergillus terreus involves two unusual type I multifunctional polyketide syntheses (PKSs). Lovastatin nonaketide synthase (LNKS), the product of the lovB gene, is an iterative PKS that interacts with LovC, a putative enoyl reductase, to catalyze the 35 separate reactions in the biosynthesis of dihydromonacolin L, a lovastatin precursor. LNKS also displays Diels-Alderase activity in vitro. Lovastatin diketide synthase (LDKS) made by lovF, in contrast, acts non-iteratively like the bacterial modular PKSs to make (2R)-2-methylbutyric acid. Then, like LNKS, LDKS interacts closely with another protein, the LovD transesterase enzyme that catalyzes attachment of the 2-methylbutyric acid to monacolin J in the final step of the lovastatin pathway. Key features of the genes for these four enzymes and others, plus the regulatory and self-resistance factors involved in lovastatin production, are also described.