Mycobacterial Enzyme Research Articles

Design, Synthesis and Biological Evaluation of Pyridyltriazole Derivatives as Potent Antitubercular Agents

In current investigation, a new series of pyridyltriazole derivatives were synthesized by conventional methods and characterized through spectroscopic techniques such as IR, NMR (1H) and mass spectroscopy. Based on colour observation and percentage of inhibition, all 24 pyridyltriazole derivatives were subjected to in vitro anti-mycobacterial testing using MABA techniques against the Mycobacterium tuberculosis (H37Rv) strain. It was found that all of the synthesized compounds were efficient in suppressing the M. tuberculosis H37Rv strain at concentrations of 1, 5 and 10 µg/mL. Among all the synthesized compounds, only 2, 3, 6, 7, 8, 11, 14, 15, 18, 20, 21, 22, 23, 24 has good anti-TB efficacy in contrast to the standard medication. According to the in silico ADME prediction, every synthesized molecule has drug-like qualities and is appropriate for oral bioavailability. Furthermore, research utilizing molecular docking have been conducted to get mechanistic understanding and molecular interactions in opposition to the mycobacterial InhA enzyme. Utilizing a molecular docking analysis, hits against specific molecular targets were found. This in silico study delved into the molecular interactions between potential compounds and the Mtbenoyl-reductaseInhA (PDB 5JFO).

A Proteins of ANL Family FACLs and FAALs, Next Anti TB Drug Targets.

The adenylating enzymes (AEs) of the ANL family contribute to the lipid synthesis process in Mycobacterium tuberculosis (MTB). FAALs (Fatty Acyl-AMP Ligase) and FACLs (Fatty Acyl-CoA Ligase) are members of the ANL enzyme family and are closely associated with the metabolism of mycobacterial lipids responsible for successful infections. Therefore, given their role in both biosynthesis and breakdown processes within fatty acid metabolism, these two groups of proteins might be potential drug targets. The growing abundance of structural, biochemical, and genetic information on mycobacterial FAAL and FACL enzymes could provide a solid foundation for the creation of next-generation anti-tuberculosis drugs, via rational drug designing.

Microwave-Assisted Synthesis and Characterization of Novel 1,3,4-Oxadiazole Derivatives and Evaluation of In Vitro Antimycobacterial Activity.

Objective The study's goal was to come up with and make a new group of 1,3,4-oxadiazole derivatives (3a-3e) and test how well they could kill Mycobacterium tuberculosis (Mtb) H37Rv strain. Additionally, molecular docking and pharmacokinetic properties were analyzed using computational software to identify potential inhibitors, followed by in vitro antimycobacterial assays. Methods A group of 1,3,4-oxadiazoles was prepared by reacting acyl hydrazides with alanine, an N-protected α-amino acid, and a small amount of POCl3. This was carried out under microwave treatment. The structural characterization of the newly synthesized compounds was performed using infrared (IR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and mass spectrometry. The in vitro antimycobacterial activity of the 1,3,4-oxadiazole derivatives (3a-3e) was assessed using the microplate Alamar Blue assay against the Mtb H37Rv strain. The synthesized compounds were subjected to molecular docking investigations in order to gain insights into their interaction mechanisms with the mycobacterial enzyme InhA (enoyl-acyl carrier protein reductase). Computational analysis of pharmacokinetic properties was performed to predict the oral bioavailability and drug-likeness of the compounds. Results All synthesized compounds inhibited the growth of Mtbat concentrations of 50 and 100 μg/mL. At a concentration of 50 μg/mL, compounds 3c and 3d exhibited the most prominent antimycobacterial action. Molecular docking results revealed that compound 3d exhibited the highest binding energy interaction with the InhA enzyme (-9.1 kcal/mol). Pharmacokinetic predictions indicated that all compounds possess favorable drug-like properties suitable for oral administration. Conclusion This study successfully synthesized a novel series of oxadiazole derivatives (3a-3e) using a microwave-assisted method with high yields. The synthesized compounds demonstrated significant antimycobacterial activity, particularly compounds 3c and 3d. Molecular docking and pharmacokinetic analyses further confirmed the potential of these compounds as promising leads for the development of anti-tubercular agents.

Identification of Chemical Scaffolds That Inhibit the Mycobacterium tuberculosis Respiratory Complex Succinate Dehydrogenase.

Drug-resistant Mycobacterium tuberculosis is a significant cause of infectious disease morbidity and mortality for which new antimicrobials are urgently needed. Inhibitors of mycobacterial respiratory energy metabolism have emerged as promising next-generation antimicrobials, but a number of targets remain unexplored. Succinate dehydrogenase (SDH), a focal point in mycobacterial central carbon metabolism and respiratory energy production, is required for growth and survival in M. tuberculosis under a number of conditions, highlighting the potential of inhibitors targeting mycobacterial SDH enzymes. To advance SDH as a novel drug target in M. tuberculosis, we utilized a combination of biochemical screening and in-silico deep learning technologies to identify multiple chemical scaffolds capable of inhibiting mycobacterial SDH activity. Antimicrobial susceptibility assays show that lead inhibitors are bacteriostatic agents with activity against wild-type and drug-resistant strains of M. tuberculosis. Mode of action studies on lead compounds demonstrate that the specific inhibition of SDH activity dysregulates mycobacterial metabolism and respiration and results in the secretion of intracellular succinate. Interaction assays demonstrate that the chemical inhibition of SDH activity potentiates the activity of other bioenergetic inhibitors and prevents the emergence of resistance to a variety of drugs. Overall, this study shows that SDH inhibitors are promising next-generation antimicrobials against M. tuberculosis.

Synthesis and in silico studies of some new pyrrolylbenzamide derivatives as antitubercular and antimicrobial agents

Eighteen new pyrrolylbenzamide derivatives (6a-6r) were synthesized by reacting N-(2,5-dimethyl- 1H-pyrrol-1-yl)-4-(2-hydrazineyl-2-oxoethoxy)benzamide (4) with substituted benzoic acids (5a-5r) in the presence of 2-(1H-benzotriazole-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate, diisopropyl ethylamine and dimethyl formamide. The produced compounds were subjected to molecular docking studies against the dihydrofolate reductase (DHFR) and InhA mycobacterial enzymes. The compounds were biologically screened for antimycobacterial, and antibacterial activities along with InhA and DHFR enzyme inhibition studies. The compounds were also analyzed for ADMET parameters. The compounds 6j, 6l, 6q, and 6r exhibited good antitubercular activity, and compounds 6j, 6l, 6q, and 6r were effective against the Gram-negative Escherichia coli strain. The compounds 6b, 6f, 6j, 6l, and 6q showed good InhA inhibition and compounds 6b, 6c, 6j, 6l, and 6q were effective against DHFR enzyme. Among the synthesized compounds 6j and 6l exhibited promising antitubercular, antibacterial, and effective InhA and DHFR enzyme inhibition values.. KEYWORDS :Benzamide, Dimethylpyrrole, Antimycobacterial activity, Antibacterial activity.

Identification of potent indolizine derivatives against Mycobacterial tuberculosis: In vitro anti-TB properties, in silico target validation, molecular docking and dynamics studies

In the current study, two sets of compounds: (E)-1-(2-(4-substitutedphenyl)-2-oxoethyl)-4-((hydroxyimino)methyl)pyridinium derivatives (3a-3e); and (E)-3-(substitutedbenzoyl)-7-((hydroxyimino)methyl)-2-substitutedindolizine-1-carboxylate derivatives (5a-5j), were synthesized and biologically evaluated against two strains of Mycobacterial tuberculosis (ATCC 25177) and multi-drug resistant (MDR) strains. Further, they were also tested in vitro against the mycobacterial InhA enzyme. The in vitro results showed excellent inhibitory activities against both MTB strains and compounds 5a-5j were found to be more potent, and their MIC values ranged from 5 to 16 μg/mL and 16–64 μg/mL against the M. tuberculosis (ATCC 25177) and MDR-TB strains, respectively. Compound 5h with phenyl and 4-fluorobenzoyl groups attached to the 2- and 3-position of the indolizine core was found to be the most active against both strains with MIC values of 5 μg/mL and 16 μg/mL, respectively. On the other hand, the two sets of compounds showed weak to moderate inhibition of InhA enzyme activity that ranged from 5 to 17 % and 10–52 %, respectively, with compound 5f containing 4-fluoro benzoyl group attached to the 3-position of the indolizine core being the most active (52 % inhibition of InhA). Unfortunately, there was no clear correlation between the InhA inhibitory activity and MIC values of the tested compounds, indicating the probability that they might have different modes of action other than InhA inhibition.Therefore, a computational investigation was conducted by employing molecular docking to identify their putative drug target(s) and, consequently, understand their mechanism of action. A panel of 20 essential mycobacterial enzymes was investigated, of which β-ketoacyl acyl carrier protein synthase I (KasA) and pyridoxal-5′-phosphate (PLP)-dependent aminotransferase (BioA) enzymes were revealed as putative targets for compounds 3a-3e and 5a-5j, respectively. Moreover, in silico ADMET predictions showed adequate properties for these compounds, making them promising leads worthy of further optimization.

A robust computational quest: Discovering potential hits to improve the treatment of pyrazinamide-resistant Mycobacterium tuberculosis.

The rise of pyrazinamide (PZA)-resistant strains of Mycobacterium tuberculosis (MTB) poses a major challenge to conventional tuberculosis (TB) treatments. PZA, a cornerstone of TB therapy, must be activated by the mycobacterial enzyme pyrazinamidase (PZase) to convert its active form, pyrazinoic acid, which targets the ribosomal protein S1. Resistance, often associated with mutations in the RpsA protein, complicates treatment and highlights a critical gap in the understanding of structural dynamics and mechanisms of resistance, particularly in the context of the G97D mutation. This study utilizes a novel integration of computational techniques, including multiscale biomolecular and molecular dynamics simulations, physicochemical and medicinal chemistry predictions, quantum computations and virtual screening from the ZINC and Chembridge databases, to elucidate the resistance mechanism and identify lead compounds that have the potential to improve treatment outcomes for PZA-resistant MTB, namely ZINC15913786, ZINC20735155, Chem10269711, Chem10279789 and Chem10295790. These computational methods offer a cost-effective, rapid alternative to traditional drug trials by bypassing the need for organic subjects while providing highly accurate insight into the binding sites and efficacy of new drug candidates. The need for rapid and appropriate drug development emphasizes the need for robust computational analysis to justify further validation through invitro and invivo experiments.

Targeting of essential mycobacterial replication enzyme DnaG primase revealed Mitoxantrone and Vapreotide as novel mycobacterial growth inhibitors.

Tuberculosis (TB) is the second leading cause of mortality after COVID-19, with a global death toll of 1.6 million in 2021. The escalating situation of drug-resistant forms of TB has threatened the current TB management strategies. New therapeutics with novel mechanisms of action are urgently required to address the current global TB crisis. The essential mycobacterial primase DnaG with no structural homology to homo sapiens presents itself as a good candidate for drug targeting. In the present study, Mitoxantrone and Vapreotide, two FDA-approved drugs, were identified as potential anti-mycobacterial agents. Both Mitoxantrone and Vapreotide exhibit a strong Minimum Inhibitory Concentration (MIC) of ≤25μg/ml against both the virulent (M.tb-H37Rv) and avirulent (M.tb-H37Ra) strains of M.tb. Extending the validations further revealed the inhibitory potential drugs in ex vivo conditions. Leveraging the computational high-throughput multi-level docking procedures from the pool of ~2700 FDA-approved compounds, Mitoxantrone and Vapreotide were screened out as potential inhibitors of DnaG. Extensive 200 ns long all-atoms molecular dynamic simulation of DnaGDrugs complexes revealed that both drugs bind strongly and stabilize the DnaG during simulations. Reduced solvent exposure and confined motions of the active centre of DnaG upon complexation with drugs indicated that both drugs led to the closure of the active site of DnaG. From this study's findings, we propose Mitoxantrone and Vapreotide as potential anti-mycobacterial agents, with their novel mechanism of action against mycobacterial DnaG.

Depletion of tRNA CCA-adding enzyme in Mycobacterium tuberculosis leads to polyadenylation of transcripts and precursor tRNAs

In reference to gene annotation, more than half of the tRNA species synthesized by Mycobacterium tuberculosis require the enzymatic addition of the cytosine-cytosine-adenine (CCA) tail, which is indispensable for amino acid charging and tRNA functionality. It makes the mycobacterial CCA-adding enzyme essential for survival of the bacterium and a potential target for novel pipelines in drug discovery avenues. Here, we described the rv3907c gene product, originally annotated as poly(A)polymerase (rv3907c, PcnA) as a functional CCA-adding enzyme (CCAMtb) essential for viability of M. tuberculosis. The depletion of the enzyme affected tRNAs maturation, inhibited bacilli growth, and resulted in abundant accumulation of polyadenylated RNAs. We determined the enzymatic activities displayed by the mycobacterial CCAMtb in vitro and studied the effects of inhibiting of its transcription in bacterial cells. We are the first to properly confirm the existence of RNA polyadenylation in mycobacteria, a previously controversial phenomenon, which we found promoted upon CCA-adding enzyme downexpression.

DprE2 is a molecular target of the anti-tubercular nitroimidazole compounds pretomanid and delamanid

Mycobacterium tuberculosis is one of the global leading causes of death due to a single infectious agent. Pretomanid and delamanid are new antitubercular agents that have progressed through the drug discovery pipeline. These compounds are bicyclic nitroimidazoles that act as pro-drugs, requiring activation by a mycobacterial enzyme; however, the precise mechanisms of action of the active metabolite(s) are unclear. Here, we identify a molecular target of activated pretomanid and delamanid: the DprE2 subunit of decaprenylphosphoribose-2’-epimerase, an enzyme required for the synthesis of cell wall arabinogalactan. We also provide evidence for an NAD-adduct as the active metabolite of pretomanid. Our results highlight DprE2 as a potential antimycobacterial target and provide a foundation for future exploration into the active metabolites and clinical development of pretomanid and delamanid.

Evaluation of Antituberculosis Activity and in Silico Properties of Oxymethylene-cyclo-1,3-diones.

Tuberculosis is a leading infectious disease that has infected one-third of the world's population and is more prevalent among people belonging to developing countries such as India and China. In the present study, a series of substituted oxymethylene-cyclo-1,3-diones was synthesized and screened for anti-tuberculosis activity against Mycobacterium tuberculosis H37Rv (M. tuberculosis). The compounds were synthesized by condensation of 1,3-cyclicdione, substituted phenols/ alcohols and triethyl orthoformate. The synthesized compounds were screened for anti-tuberculosis activity against M.tuberculosis H37Rv using Middlebrook 7H9 broth assay. Results demonstrated that among the synthesized library of molecules, two compounds 2-(2-hydroxyphenoxymethylene)-5,5-dimethylcyclohexane-1,3-dione and 5,5-dimethyl-2-(2-trifluoromethylphenoxymethylene)cyclohexane-1,3-dione were found to be most active against M. tuberculosis (MICs of 1.25 μg/mL-1 ). The MICs of 2-(2,4-difluoro-phenoxymethylene)-5,5-dimethylcyclohexane-1,3-dione and 2-(2-bromophenoxymethylene)-5,5-dimethylcyclohexane-1,3-dione were found to be 5 and 10 μg mL-1 , respectively. Data from the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay showed that all the four most active compounds did not exhibit cytotoxicity against human cell lines. Molecular docking studies revealed that the most active compound targets mycobacterial InhA enzyme. In summary, the present study demonstrates the methodology for the synthesis of oxymethylene-cyclo-1,3-diones and identified two potential anti-tuberculosis compounds.

Inhibition Studies on Human and Mycobacterial Carbonic Anhydrases with N-((4-Sulfamoylphenyl)carbamothioyl) Amides.

A library of structurally diverse N-((4-sulfamoylphenyl)carbamothioyl) amides was synthesized by selective acylation of easily accessible 4-thioureidobenzenesulfonamide with various aliphatic, benzylic, vinylic and aromatic acyl chlorides under mild conditions. Inhibition of three α-class cytosolic human (h) carbonic anhydrases (CAs) (EC 4.2.1.1); that is, hCA I, hCA II and hCA VII and three bacterial β-CAs from Mycobacterium tuberculosis (MtCA1-MtCA3) with these sulfonamides was thereafter investigated in vitro and in silico. Many of the evaluated compounds displayed better inhibition against hCA I (KI = 13.3-87.6 nM), hCA II (KI = 5.3-384.3 nM), and hCA VII (KI = 1.1-13.5 nM) compared with acetazolamide (AAZ) as the control drug (KI values of 250, 12.5 and 2.5 nM, respectively, against hCA I, hCA II and hCA VII). The mycobacterial enzymes MtCA1 and MtCA2 were also effectively inhibited by these compounds. MtCA3 was, on the other hand, poorly inhibited by the sulfonamides reported here. The most sensitive mycobacterial enzyme to these inhibitors was MtCA2 in which 10 of the 12 evaluated compounds showed KIs (KI, the inhibitor constant) in the low nanomolar range.

Nitrobenzoates and Nitrothiobenzoates with Activity against M. tuberculosis.

Esters of weak acids have shown improved antimycobacterial activity over the corresponding free acids and nitro benzoates in particular have previously shown to have a very intriguing activity. To expand the potential of nitro-derivatives of benzoic acid as antimycobacterial drugs and explore the effects of various structural features on the activity of these compounds, we have obtained a library of 64 derivatives containing esters and thioesters of benzoates and studied their activity against M. tuberculosis, the stability of the compounds, their activation by mycobacterial enzymes and the potential cytotoxicity against human monocytic THP-1 cell line. Our results showed that the most active compounds are those with an aromatic nitro substitution, with the 3,5-dinitro esters series being the most active. Also, the greater antitubercular activity for the nitro derivatives was shown to be unrelated to their pKa values or hydrolysis rates. Given the conventional relationship between nitro-containing substances and toxicity, one might anticipate that the great antimicrobial activity of nitro compounds would be associated with high toxicity; yet, we have not found such a relationship. The nitrobenzoate scaffold, particularly the 3,5-dinitrobenzoate scaffold, merits further investigation, because it has the potential to generate future antimycobacterial agents with improved activity.

In-Silico Drug Design And Adme Studies Of Substituted 1, 3, 4-Oxadiazole Analogues As Potent Mycobacterial Dpre1 Enzyme Inhibitors

Mycobacterial infections and multidrug-resistant (MDR) strains of Mycobacterium generate high mortality, this has triggered the scientific community to search for novel, effective, and safer therapeutics. A series of 4, 5-disubstituted-1, 3, 4-oxadiazole derivatives were screened for mycobacterial activity against H37Rv, MDR and XDR strains. To recognize the mechanism of action of these compounds and to identify their supposed drug target, molecular docking and dynamics studies were employed against DprE1 mycobacterial enzyme, which is reported to be an essential enzyme for mycobacterial growth and survival. The ADME and drug-likeness properties revealed that all the compounds have good pharmacokinetic properties. All the compounds have high affinity towards the enzyme. The newly synthesized derivatives were confirmed through FT-IR, 1 H-NMR, and LCMS. In-vitro microplate alamar blue assay (MABA) to determine the MIC (minimum inhibitory concentration) values against Mycobacterium tuberculosis H37Rv was performed for the synthesized compounds. The synthesized compounds 2A, 3A, 4A, 5A and 6A exhibited promising activity against Mycobacterium tuberculosis.

The Mycobacterium tuberculosis prolyl dipeptidyl peptidase cleaves the N-terminal peptide of the immunoprotein CXCL-10.

Dipeptidyl peptidases constitute a class of non-classical serine proteases that regulate an array of biological functions, making them pharmacologically attractive enzymes. With this work, we identified and characterized a dipeptidyl peptidase from Mycobacterium tuberculosis (MtDPP) displaying a strong preference for proline residues at the P1 substrate position and an unexpectedly high thermal stability. MtDPP was also characterized with alanine replacements of residues of its active site that yielded, for the most part, loss of catalysis. We show that MtDPP catalytic activity is inhibited by well-known human DPP4 inhibitors. Using MALDI-TOF mass spectrometry we also describe that invitro, MtDPP mediates the truncation of the C-X-C motif chemokine ligand10, indicating a plausible role in immune modulation for this mycobacterial enzyme.

Trifluoromethylcinnamanilide Michael Acceptors for Treatment of Resistant Bacterial Infections

A series of thirty-two anilides of 3-(trifluoromethyl)cinnamic acid (series 1) and 4-(trifluoromethyl)cinnamic acid (series 2) was prepared by microwave-assisted synthesis. All the compounds were tested against reference strains Staphylococcus aureus ATCC 29213 and Enterococcus faecalis ATCC 29212 and resistant clinical isolates of methicillin-resistant S. aureus (MRSA) and vancomycin-resistant E. faecalis (VRE). All the compounds were evaluated in vitro against Mycobacterium smegmatis ATCC 700084 and M. marinum CAMP 5644. (2E)-3-[3-(Trifluoromethyl)phenyl]-N-[4-(trifluoromethyl)phenyl]prop-2-enamide (1j), (2E)-N-(3,5-dichlorophenyl)-3-[3-(trifluoromethyl)phenyl]prop-2-enamide (1o) and (2E)-N-[3-(trifluoromethyl)phenyl]-3-[4-(trifluoromethyl)-phenyl]prop-2-enamide (2i), (2E)-N-[3,5-bis(trifluoromethyl)phenyl]-3-[4-(trifluoromethyl)phenyl]-prop-2-enamide (2p) showed antistaphylococcal (MICs/MBCs 0.15-5.57 µM) as well as anti-enterococcal (MICs/MBCs 2.34-44.5 µM) activity. The growth of M. marinum was strongly inhibited by compounds 1j and 2p in a MIC range from 0.29 to 2.34 µM, while all the agents of series 1 showed activity against M. smegnatis (MICs ranged from 9.36 to 51.7 µM). The performed docking study demonstrated the ability of the compounds to bind to the active site of the mycobacterial enzyme InhA. The compounds had a significant effect on the inhibition of bacterial respiration, as demonstrated by the MTT assay. The compounds showed not only bacteriostatic activity but also bactericidal activity. Preliminary in vitro cytotoxicity screening was assessed using the human monocytic leukemia cell line THP-1 and, except for compound 2p, all effective agents did show insignificant cytotoxic effect. Compound 2p is an interesting anti-invasive agent with dual (cytotoxic and antibacterial) activity, while compounds 1j and 1o are the most interesting purely antibacterial compounds within the prepared molecules.

Structural investigation and gene deletion studies of mycobacterial oligoribonuclease reveal modulation of c-di-GMP-mediated phenotypes

Cyclic-di-GMP (c-di-GMP) is a ubiquitous bacterial second messenger required for normal physiology as well as survival under hypoxic and reductive stress conditions of mycobacterial cells. Complete degradation of c-di-GMP is necessary for signal termination and maintaining its homeostasis inside the cells. Homeostasis of c-di-GMP in mycobacteria is brought about by the bifunctional diguanylate cyclase (DGC) that synthesizes c-di-GMP from two molecules of GTP and also catalyses the asymmetric cleavage of c-di-GMP to linear pGpG through its phosphodiesterase activity. However, the mycobacterial enzyme for the last step of degradation from pGpG to GMP has not been characterized thus far. Here, we present the identification of oligoribonuclease (Orn) as the most likely phosphodiesterase to degrade pGpG to GMP through AlphaFold-empowered structural homology that exhibited in vitro phosphodiesterase activity on pGpG substrates. In order to understand the physiological role of Orn in mycobacteria, we created a deletion mutant of orn in M. smegmatis and analysed the phenotypes that are associated with c-di-GMP signaling. We find that orn plays important roles in vivo and is required not only for proper growth of M. smegmatis in normal and stress conditions but also for biofilm formation.

Direct capture, inhibition and crystal structure of HsaD (Rv3569c) from M. tuberculosis.

A hallmark of Mycobacterium tuberculosis (M. tb), the aetiologic agent of tuberculosis, is its ability to metabolise host-derived lipids. However, the enzymes and mechanisms underlying such metabolism are still largely unknown. We previously reported that the Cyclophostin & Cyclipostins (CyC) analogues, a new family of potent antimycobacterial molecules, react specifically and covalently with (Ser/Cys)-based enzymes mostly involved in bacterial lipid metabolism. Here, we report the synthesis of new CyC alkyne-containing inhibitors (CyCyne ) and their use for the direct fishing of target proteins in M. tb culture via bio-orthogonal click-chemistry activity-based protein profiling (CC-ABPP). This approach led to the capture and identification of a variety of enzymes, and many of them involved in lipid or steroid metabolisms. One of the captured enzymes, HsaD (Rv3569c), is required for the survival of M. tb within macrophages and is thus a potential therapeutic target. This prompted us to further explore and validate, through a combination of biochemical and structural approaches, the specificity of HsaD inhibition by the CyC analogues. We confirmed that the CyC bind covalently to the catalytic Ser114 residue, leading to a total loss of enzyme activity. These data were supported by the X-ray structures of four HsaD-CyC complexes, obtained at resolutions between 1.6 and 2.6 Å. The identification of mycobacterial enzymes directly captured by the CyCyne probes through CC-ABPP paves the way to better understand and potentially target key players at crucial stages of the bacilli life cycle.

Molecular Docking Interactions with Mycobacterial ATP and Polyketide-13 Synthase Enzymes of Phytoconstituents Isolated from Entada abyssinica Stem Bark

The search for novel therapies for tuberculosis continues due to the emergence of resistant strains, adverse drug reactions, and potential drug-drug interactions of antitubercular drugs. This study was undertaken to identify compounds from Entada abyssinica, a plant used by herbalists in East Africa for the management of symptoms of tuberculosis. An extract of shade-dried E. abyssinica stem bark was prepared by maceration in a mixture of acetone and methanol in the ratio of 3:2. Column and thin layer chromatography were used to isolate pure compounds. The structures of the compounds were elucidated using nuclear magnetic resonance and infrared spectroscopy. The compounds were further studied using in silico tools to predict their binding affinities, descriptors of pharmacokinetics, and toxicity. Seven known compounds: 2,3-dihydroxypropyltriacontanoate (1), 1',26'-bis-(2,3-dihydroxypropyl) hexacosanedioate (2), stigmasterol 3-O--D-glucopyranoside (3), sitosterol 3-O--D-glucopyranoside (4), Spinasterol 3-O--D-glucopyranoside (5), stigmasterol (6) and spinasterol (7) were isolated. Compounds 1 and 2 had better binding affinities (-27.7374 and -28.5726 Kcal/mol) than the bedaquiline (-22.9042 Kcal/mol) for ATP. All isolated compounds had better binding affinities (between -21.4357 and -18.7809 Kcal/mol) than isoniazid (-10.8307 Kcal/mol) for polyketide-13 synthase enzymes. The compounds showed variable but promising pharmacokinetic properties with minimum toxicity. E. abyssinica stem bark contains phytochemicals with promising antimycobacterial activity via inhibition of the ATP and polyketide-13 synthase enzymes. In vitro and in vivo studies are recommended to validate the predicted antimycobacterial activity as well as the pharmacokinetics and toxicity profiles.

Benzoic Acid Derivatives as Prodrugs for the Treatment of Tuberculosis.

One interesting approach to fight tuberculosis is the use of prodrugs that often have shown improved biological activities over drugs with poor absorption or difficulty to cross membranes. Previous studies demonstrate that weak acids such as benzoic acid, present antimycobacterial activity. Moreover, esters of those acids revealed to be a viable alternative since they may diffuse more easily through the cell membranes. Previously we showed that mycobacteria can easily activate benzoic acid esters by conversion to the corresponding acid. Since Zhang postulated that the activity of the acids can be dependent on their pKa, we set up to synthesize a library of benzoates with different electron withdrawing groups (4-chloro, 2,6-dichloro, 3,5-dichloro, 4-nitro, and 3,5 dinitro), to modulate pKa of the liberated acid and different alkoxy substituents (propyl, hexyl, and phenyl) to modulate their lipophilicity, and tested the activity of the esters and the corresponding free acids against mycobacteria. We also studied the activation of the esters by mycobacterial enzymes and the stability of the compounds in buffer and plasma. We concluded that all the benzoates in our study can be activated by mycobacterial enzymes and that the phenyl and hexyl esters presented higher activity than the corresponding free acids, with the nitrobenzoates, and especially the dinitrobenzoates, showing very interesting antitubercular activity that deserve further exploration. Our results did not show a correlation between the activity and the pKa of the acids.