Mycolic Acid Biosynthesis Research Articles

Development of Mycobacterium tuberculosis Enoyl Acyl Reductase (InhA) Inhibitors: A Mini-Review

This review article delves into the critical role of Enoyl acyl carrier protein Reductase (InhA; ENR), a vital enzyme in the NADH-dependent acyl carrier protein reductase family, emphasizing its significance in fatty acid synthesis and, more specifically, the biosynthesis of mycolic acid. The primary objective of this literature review is to elucidate diverse scaffolds and their developmental progression targeting InhA inhibition, thereby disrupting mycolic acid biosynthesis. Various scaffolds, including thiourea, piperazine, thiadiazole, triazole, quinazoline, benzamide, rhodanine, benzoxazole, and pyridine, have been systematically explored for their potential as InhA inhibitors. Noteworthy findings highlight thiadiazole and triazole derivatives, demonstrating promising IC50 values within the nanomolar concentration range. The review offers comprehensive insights into InhA's structure, structure-activity relationships, and a detailed overview of distinct scaffolds as effective inhibitors of InhA.

Pharmacophore guided deep learning approach to identify novel inhibitors targeting mycobacterial polyketide synthase Pks13-TE domain

Tuberculosis (TB), an enduring global health challenge, persists due to the rise of drug-resistant Mycobacterium tuberculosis (MTB) strains. Among potential therapeutic targets, Pks13, a protein crucial for mycolic acid biosynthesis, is key for Mtb's virulence and survival. This study employed a pharmacophore-based drug design approach, employing the Pharmacophore-Guided Molecular Generation (PGMG) tool to target Pks13 inhibitors. Aromatic, hydrophobic, positive ion and hydrogen bond acceptors pharmacophoric features were identified from co-crystal ligands. Candidate compounds underwent evaluation of pharmacokinetic properties with the ADMET_AI tool. Further refinement involved molecular docking with PLANTS software, absolute binding free energy calculations via KDeep, and toxicity assessments using eToxPred. MM-GBSA, PCA, DCCM, and FEL were incorporated to validate and refine inhibitors accurately. From this analysis, we discovered five novel hit molecules. These includes, ethyl (S)-4-(4-(2-(2-(cyclohexylamino)-2-oxoethoxy)-2-oxoethoxy)phenyl)-6-methyl-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate (Pk1), 2-(4-((2‑butyl‑6-pivalamido-1H-benzo [d]imidazol-1-yl)methyl)phenoxy)acetic acid (Pk2), (S)-2-(4-(4-cyclopentyl-5-(1-((6-methyl-2-morpholinopyrimidin-4-yl)amino)ethyl)-4H-1,2,4-triazol-3-yl)phenoxy)acetic acid (Pk3), (E)-2-(4-oxo-5-(4-((6-phenylpyridin-2-yl)methoxy)benzylidene)-2-thioxothiazolidin-3-yl)acetic acid (Pk4), and N-((1R,4r)-4-(((1R,2r,3S,5S,7S)-5‑hydroxy adamantan-2-yl)oxy)cyclohexyl)-4-morpholinobenzamide (Pk5). We conclude that the screened hit compounds may act as potential inhibitors targeting Pks13 and further preclinical and clinical studies may pave the way for developing them as effective therapeutic agents for the treatment of MTB.

The conserved σD envelope stress response monitors multiple aspects of envelope integrity in corynebacteria.

The cell envelope fortifies bacterial cells against antibiotics and other insults. Species in the Mycobacteriales order have a complex envelope that includes an outer layer of mycolic acids called the mycomembrane (MM) and a cell wall composed of peptidoglycan and arabinogalactan. This envelope architecture is unique among bacteria and contributes significantly to the virulence of pathogenic Mycobacteriales like Mycobacterium tuberculosis. Characterization of pathways that govern envelope biogenesis in these organisms is therefore critical in understanding their biology and for identifying new antibiotic targets. To better understand MM biogenesis, we developed a cell sorting-based screen for mutants defective in the surface exposure of a porin normally embedded in the MM of the model organism Corynebacterium glutamicum. The results revealed a requirement for the conserved σD envelope stress response in porin export and identified MarP as the site-1 protease, respectively, that activate the response by cleaving the membrane-embedded anti-sigma factor. A reporter system revealed that the σD pathway responds to defects in mycolic acid and arabinogalactan biosynthesis, suggesting that the stress response has the unusual property of being induced by activating signals that arise from defects in the assembly of two distinct envelope layers. Our results thus provide new insights into how C. glutamicum and related bacteria monitor envelope integrity and suggest a potential role for members of the σD regulon in protein export to the MM.

Dissecting the Ca2+ dependence of DesA1 function in Mycobacterium tuberculosis.

Mycobacterium tuberculosis (M. tb) has a complex cell wall, composed largely of mycolic acids, that are crucial to its structural maintenance. The M. tb desaturase A1 (DesA1) is an essential Ca2+-binding protein that catalyses a key step in mycolic acid biosynthesis. To investigate the structural and functional significance of Ca2+ binding, we introduced mutations at key residues in its Ca2+-binding βγ-crystallin motif to generate DesA1F303A, E304Q, and F303A-E304Q. Complementation of a conditional ΔdesA1 strain of Mycobacterium smegmatis, with the Ca2+ non-binders F303A or F303A-E304Q, failed to rescue its growth phenotype; these complements also exhibited enhanced cell wall permeability. Our findings highlight the criticality of Ca2+ in DesA1 function, and its implicit role in the maintenance of mycobacterial cellular integrity.

In silico analysis and characterization of potential inhibitors of MmaA3, a methoxy mycolic acid synthase from Mycobacterium tuberculosis

The emergence of the multi-and extensively drug-resistant (MDR and XDR) strains of Mycobacterium tuberculosis (M.tb), necessitates paradigm-shifting therapeutic approaches. The impermeable waxy lipid layer, primarily composed of mycolic acids, is a key factor in conferring resistance to conventional drugs. This study introduces a novel strategy to combat drug resistance by targeting Methoxy mycolic acid synthase 3 (MmaA3), a critical enzyme in the mycolic acid biosynthesis pathway. MmaA3 is responsible for the O-methylation of hydroxymycolate precursors and emerges as a promising therapeutic target. Through homology-based modeling, we generated a three-dimensional structure of MmaA3, providing crucial insights into its structural characteristics. High throughput virtual screening was performed against the MmaA3 model, using diverse sources: knowledge-based, FDA-approved Drugbank, and Asinex-Elite libraries. Through rigorous computational analyses, including binding affinity assessments, molecular interactions analysis, and binding free energy calculations, potential inhibitors of MmaA3 have been identified. Subsequent validation studies evaluated the stability of top protein-ligand complexes, and free energy calculations using molecular dynamics simulations. The stability of complexes within the catalytic site was confirmed through RMSD and RMSF profile analyses. Furthermore, binding free energy calculations using the MM-GBSA approach revealed significant binding affinity of identified ligands for MmaA3 target protein, comparable to its substrate/cofactors. These findings underscore the potential of the proposed molecules as candidates for further experimental exploration, offering promising avenues for the development of effective inhibitors against M.tb. Overall, our research contributes to significantly advancing the formulation of progressive therapeutic strategies in combating drug-resistant tuberculosis. Communicated by Ramaswamy H. Sarma

HadBD dehydratase from Mycobacterium tuberculosis fatty acid synthase type II: A singular structure for a unique function.

Worldwide, tuberculosis is the second leading infectious killer and multidrug resistance severely hampers disease control. Mycolic acids are a unique category of lipids that are essential for viability, virulence, and persistence of the causative agent, Mycobacterium tuberculosis (Mtb). Therefore, enzymes involved in mycolic acid biosynthesis represent an important class of drug targets. We previously showed that the (3R)-hydroxyacyl-ACP dehydratase (HAD) protein HadD is dedicated mainly to the production of ketomycolic acids and plays a determinant role in Mtb biofilm formation and virulence. Here, we discovered that HAD activity requires the formation of a tight heterotetramer between HadD and HadB, a HAD unit encoded by a distinct chromosomal region. Using biochemical, structural, and cell-based analyses, we showed that HadB is the catalytic subunit, whereas HadD is involved in substrate binding. Based on HadBDMtb crystal structure and substrate-bound models, we identified determinants of the ultra-long-chain lipid substrate specificity and revealed details of structure-function relationship. HadBDMtb unique function is partly due to a wider opening and a higher flexibility of the substrate-binding crevice in HadD, as well as the drastically truncated central α-helix of HadD hotdog fold, a feature described for the first time in a HAD enzyme. Taken together, our study shows that HadBDMtb , and not HadD alone, is the biologically relevant functional unit. These results have important implications for designing innovative antivirulence molecules to fight tuberculosis, as they suggest that the target to consider is not an isolated subunit, but the whole HadBD complex.

Azetidines Kill Multidrug-Resistant Mycobacterium tuberculosis without Detectable Resistance by Blocking Mycolate Assembly.

Tuberculosis (TB) is the leading cause of global morbidity and mortality resulting from infectious disease, with over 10.6 million new cases and 1.4 million deaths in 2021. This global emergency is exacerbated by the emergence of multidrug-resistant MDR-TB and extensively drug-resistant XDR-TB; therefore, new drugs and new drug targets are urgently required. From a whole cell phenotypic screen, a series of azetidines derivatives termed BGAz, which elicit potent bactericidal activity with MIC99 values <10 μM against drug-sensitive Mycobacterium tuberculosis and MDR-TB, were identified. These compounds demonstrate no detectable drug resistance. The mode of action and target deconvolution studies suggest that these compounds inhibit mycobacterial growth by interfering with cell envelope biogenesis, specifically late-stage mycolic acid biosynthesis. Transcriptomic analysis demonstrates that the BGAz compounds tested display a mode of action distinct from the existing mycobacterial cell wall inhibitors. In addition, the compounds tested exhibit toxicological and PK/PD profiles that pave the way for their development as antitubercular chemotherapies.

Virtual screening and identification of promising therapeutic compounds against drug-resistant Mycobacterium tuberculosis β-ketoacyl-acyl carrier protein synthase I (KasA)

The emergence of new Mycobacterium tuberculosis (Mtb) strains resistant to the key drugs currently used in the clinic for tuberculosis treatment can substantially reduce the probability of therapy success, causing the relevance and importance of studies on the development of novel potent antibacterial agents targeting different vulnerable spots of Mtb. In this study, 28,860 compounds from the library of bioactive molecules were screened to identify novel potential inhibitors of β-ketoacyl-acyl carrier protein synthase I (KasA), one of the key enzymes involved in the biosynthesis of mycolic acids of the Mtb cell wall. In doing so, we used a structure-based virtual screening approach to drug repurposing that included high-throughput docking of the C171Q KasA enzyme with compounds from the library of bioactive molecules including the FDA-approved drugs and investigational drug candidates, assessment of the binding affinity for the docked ligand/C171Q KasA complexes, and molecular dynamics simulations followed by binding free energy calculations. As a result, post-modeling analysis revealed 6 top-ranking compounds exhibiting a strong attachment to the malonyl binding site of the enzyme, as evidenced by the values of binding free energy which are significantly lower than those predicted for the KasA inhibitor TLM5 used in the calculations as a positive control. In light of the data obtained, the identified compounds are suggested to form a good basis for the development of new antitubercular molecules of clinical significance with activity against the KasA enzyme of Mtb. Communicated by Ramaswamy H. Sarma

Cytotoxicity and gene expression studies in understanding the mechanism on antimycobacterial properties of methanolic leaf extract of Acalypha indica Linn.

Despite the availability of effective antituberculosis medication, tuberculosis (TB) remains a serious global health concern, raising the demand for low-after effect drug alternative. This study aims to explore the anti-mycobacterial potency of Acalypha indica Linn. on Mycobacterium tuberculosis using Mycobacterium smegmatis as a model and thereby uncover its mechanism. Characterization of bioactive phytocompounds and their cumulative effects were studied through both biochemical and molecular approaches. The antimycobacterial efficacy was screened by cell viability assay and IC50. FE-SEM and qRT-PCR were used to study the effect of A. indica leaf methanolic extract (AILME) on cell integrity and mycolic acid synthesis pathway. This study reports AILME to be the most effective solvent-extract combination which showed >40 % cell inhibition from 25 µg mL−1 onwards at 24 hr. AILME showed >80 % antioxidant potential, lowest IC50 of 48.24 µg mL−1 and a MIC value of 200 µg mL−1 at 24 hr. The FE-SEM analysis of the AILME treated bacterial cells showed significant morphological damage which supports the results of antimycobacterial activity. The gene expression study revealed that AILME inhibited the expression of inhA and mtrA genes involved in mycolic acid biosynthesis pathway and cell wall integrity, respectively. The bioactive phytocompounds characterised through GCMS and HR-LCMS revealed about nineteen potent anti-TB compounds like malic acid, catechin, pyrrolidine, hexadecanoic acid, quercetin etc. that might supervise the role behind the antimycobacterial effect of the herb. This study reveals that AILME possesses strong antimycobacterial action by impeding the formation of mycolic acid biosynthesis pathway and disorganization of cell wall. Presence of anti-TB phytocompounds in abundance suggest its potential chemotherapeutic nature against M. tuberculosis.

Computational insights into potential marine natural products as selective inhibitors of Mycobacterium tuberculosis InhA: A structure-based virtual screening study

Several factors are associated with the emergence of drug resistance mechanisms, such as impermeable cell walls, gene mutations, and drug efflux systems. Consequently, bacteria acquire resistance, leading to a decrease in drug efficacy. A new and innovative strategy is required to combat drug resistance in tuberculosis (TB) effectively. Therefore, targeting the mycolic acid biosynthesis pathway, which is involved in synthesising mycolic acids (MAs), essential structural components responsible for mycobacterial pathogenicity, has garnered interest in TB research and the concept of drug resistance. In this context, InhA, which plays a crucial role in the fatty acid synthase-II (FAS-II) system of the MA biosynthetic pathway, was selected as a druggable target for screening investigation. To identify potential lead molecules against InhA, diverse marine natural products (MNPs) were collected from the comprehensive marine natural products database (CMNPD). Virtual screening studies aided in selecting potential lead molecules that best fit within the substrate-binding pocket (SBP) of InhA, forming crucial hydrogen bond interaction with the catalytic residue Tyr158. Three MNPs, CMNPD30814, CMNPD1702, and CMNPD27355, were chosen as prospective alternative molecules due to their favorable pharmacokinetic properties and lack of toxicity according to ProTox-II predictions. Additionally, improved reactivity of the MNPs was observed in the results of density functional theory (DFT) studies. Furthermore, comparative molecular dynamics simulation (MDS), principal component (PC)-based free energy landscape (FEL) analysis, and molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) were employed to show enhanced structural stability, increased H-bond potential, and high binding affinity toward the target InhA. Moreover, the hot spot residues that contributed to the high binding energy profile and anchored the stability of the complexes were revealed with their individual interaction energy. The computational insights from this study provide potential avenues to combat TB through the multifaceted mode of action of these marine lead molecules, which can be further explored in future experimental investigations.

Reassessing the putative molecular Target(s) of potent antitubercular 2-(Alkylsulfonyl)acetamides

Simple alkyl-sulfonylacetamides have potent antitubercular activity and significantly decrease mycolic acid levels in mycobacteria. Although these compounds were originally designed to inhibit the ketoacyl synthase domain of fatty acid synthase, structure-activity relationships and biochemical evidence do not fully support fatty acid synthase as the target. In 2004, an enzyme family involved in the activation and transfer of fatty acids as acyl-adenylates was identified in mycobacteria, separate from the universal acetyl-CoA carrier mechanism. These fatty acyl-AMP ligases (FAAL), encoded by the FadD family play important roles in the biosynthesis of mycolic acids along with fatty acid metabolism and are hypothesised here to be the molecular target of the sulfonylacetamides. Due to structural similarities with the ligase's natural substrate, it is believed these compounds are exerting action via competitive inhibition of these highly potent molecular targets. The primary aim of this investigation was to synthesize an extended library of sulfonylacetamide derivatives, building upon existing structural activity relations to validate the molecular mechanism with the aid of molecular modelling, while also attempting to explore novel structural isosteres for further drug design and development. Sulfonylacetamide derivatives were modified based on the putative molecular target resulting in derivatives with improved activities towards Mycobacteriumtuberculosis (H37Rv). The most active novel derivatives reported were 19, 22b, 22c and 46 displaying MIC90 levels of 1.4, 16.0, 13.0 and 5.9 μg/mL, respectively.

Genome sequence of Gordonia alkaliphila strain WW102, isolated from influent wastewater at a research center with multiple-species research animal facilities.

Gordonia alkaliphila is a little known mesophilic Gram-positive rod-shaped bacterium. We report the 3.85-Mbp genome sequence of G. alkaliphila strain WW102, isolated from wastewater at a research center with multiple-species laboratory animal facilities. The genome predicted FadD32 gene clusters that are involved in the biosynthesis of mycolic acids as found in Mycobacterium tuberculosis.

A Computational Study on the Structural Prediction of InhA Inhibitors as Antimycobacterial Agents

InhA is an enoyl acyl carrier reductase that catalyzes the chemo-selective reduction of its 2-trans-enoyl-ACP substrate. The pharmacological effects of the frontline medications used in the treatment of tuberculosis are elicited by inhibiting the enzyme InhA, which disrupts the mycolic acid biosynthesis pathway. The present study involves development of ligand-based pharmacophore model, docking studies, generation of 3D-QSAR model, and molecular dynamic simulation studies of virtually screened putative InhA inhibitors. The best field-based 3D-QSAR model was validated using partial least-square regression (PLS) method with high regression coefficient for training set (R 2) = 0.9256 and test set (R 2) = 0.7542, cross-validated coefficient (r cv 2) = 0.72 and R 2 pred = 0.9764. Also, virtual screening yielded compounds 4, 25, 1, and 30 exhibiting appreciable interactions (docking scores −5.972, −3.819, −3.801, and −3.701, respectively with InhA synthetase; PDB ID: 1BVR). Further, ADMET studies supported drug-like potential of compounds 25, 1, and 30 whereas compound 4 showed negligible human oral absorption. The molecular dynamic simulation studies of the top scored molecule 25 suggested stability of 25-1BVR complex over the course of simulation run. Therefore, this work can be helpful for future discovery of novel InhA inhibitors against drug-resistant tuberculosis.

Discovery of new diaryl ether inhibitors against Mycobacterium tuberculosis targeting the minor portal of InhA

Tuberculosis (TB) caused by Mycobacterium tuberculosis (Mtb) affects 10 million people each year and the emergence of resistant TB augurs for a growing incidence. In the last 60 years, only three new drugs were approved for TB treatment, for which resistances are already emerging. Therefore, there is a crucial need for new chemotherapeutic agents capable of eradicating TB. Enzymes belonging to the type II fatty acid synthase system (FAS-II) are involved in the biosynthesis of mycolic acids, cell envelope components essential for mycobacterial survival. Among them, InhA is the primary target of isoniazid (INH), one of the most effective compounds to treat TB. INH acts as a prodrug requiring activation by the catalase-peroxidase KatG, whose mutations are the major cause for INH resistance. Herein, a new series of direct InhA inhibitors were designed based on a molecular hybridization approach. They exhibit potent inhibitory activities of InhA and, for some of them, good antitubercular activities. Moreover, they display a low toxicity on human cells. A study of the mechanism of action of the most effective molecules shows that they inhibit the biosynthesis of mycolic acids. The X-ray structures of two InhA/NAD+/inhibitor complexes have been obtained showing a binding mode of a part of the molecule in the minor portal, rarely seen in the InhA structures reported so far.

Facing Antitubercular Resistance: Identification of Potential Direct Inhibitors Targeting InhA Enzyme and Generation of 3D-pharmacophore Model by in silico Approach.

The enoyl-acyl carrier protein reductase (InhA) is one of the important key enzymes employed in mycolic acids biosynthesis pathway and an important component of mycobacterial cell walls. This enzyme has also been identified as major target of isoniazid drug, except that isoniazid needs to be activated first by the catalase peroxidase (KatG) protein to form the isonicotinoyl-NAD (INH-NAD) adduct that inhibits the action of InhA enzyme. However, this activation becomes more difficult and unreachable with the problem of mutation-related resistance caused mainly by acquired mutations in KatG and InhA protein. Our main interest in this study is to identify direct InhA inhibitors using computer-aided drug design. Computer-aided drug design was used to solve this problem by applying three different approaches including mutation impact modelling, virtual screening and 3D-pharmacophore search. A total of 15 mutations were collected from the literature, then a 3D model was generated for each of them and their impact was predicted. Of the 15 mutations, 10 were found to be deleterious and have a direct effect on flexibility, stability and SASA of the protein. In virtual screening, from 1,000 similar INH-NAD analogues obtained by the similarity search method, 823 compounds passed toxicity filter and drug likeness rules, which were then docked to the wild-type of InhA protein. Subsequently, 34 compounds with binding energy score better than that of INH-NAD were selected and docked against the 10 generated mutated models of InhA. Only three leads showed a lower binding affinity better than the reference. The 3D-pharmacophore model approach was used to identify the common features between those three compounds by generating a pharmacophoric map. The result of this study may pave the way to develop more potent mutant-specific inhibitors to overcome this resistance.

MarR-Dependent Transcriptional Regulation of mmpSL5 Induces Ethionamide Resistance in Mycobacterium abscessus.

Mycobacterium abscessus (Mabs) is an emerging nontuberculosis mycobacterial (NTM) pathogen responsible for a wide variety of respiratory and cutaneous infections that are difficult to treat with standard antibacterial therapy. Mabs has a high degree of both innate and acquired antibiotic resistance to most clinically relevant drugs, including standard anti-mycobacterial agents. Ethionamide (ETH), an inhibitor of mycolic acid biosynthesis, is currently utilized as a second-line agent for treating multidrug-resistant tuberculosis infections. Here, we show that ETH displays activity against clinical strains of Mabs in vitro at concentrations that are >100× lower than other mycolic acid targeting drugs. Using transposon mutagenesis followed by transposon sequencing (Tn-Seq) and whole-genome sequencing of spontaneous ETH-resistant mutants, we identified MAB_2648c as a genetic determinant of ETH sensitivity in Mabs. MAB_2648c encodes a MarR family transcriptional regulator of the TetR class of regulators. We show that MAB_2648c represses expression of MAB_2649 (mmpS5) and MAB_2650 (mmpL5). Further, we show that derepression of these genes in MAB_2648c mutants confers resistance to ETH, but not other antibiotics. To identify determinants of resistance that may be shared across antibiotics with distinct mechanisms of action, we also performed Tn-Seq during treatment with amikacin and clarithromycin, drugs currently used clinically to treat Mabs. We found very little overlap in genes that modulate the sensitivity of Mabs to all three antibiotics, suggesting a high degree of specificity for resistance mechanisms in this emerging pathogen.

Recent Advances in Anti-Tuberculosis Drug Discovery Based on Hydrazide-Hydrazone and Thiadiazole Derivatives Targeting InhA.

Tuberculosis is an extremely serious problem of global public health. Its incidence is worsened by the presence of multidrug-resistant (MDR) strains of Mycobacterium tuberculosis. More serious forms of drug resistance have been observed in recent years. Therefore, the discovery and/or synthesis of new potent and less toxic anti-tubercular compounds is very critical, especially having in mind the consequences and the delays in treatment caused by the COVID-19 pandemic. Enoyl-acyl carrier protein reductase (InhA) is an important enzyme involved in the biosynthesis of mycolic acid, a major component of the M. tuberculosis cell wall. At the same time, it is a key enzyme in the development of drug resistance, making it an important target for the discovery of new antimycobacterial agents. Many different chemical scaffolds, including hydrazide hydrazones and thiadiazoles, have been evaluated for their InhA inhibitory activity. The aim of this review is to evaluate recently described hydrazide-hydrazone- and thiadiazole-containing derivatives that inhibit InhA activity, resulting in antimycobacterial effects. In addition, a brief review of the mechanisms of action of currently available anti-tuberculosis drugs is provided, including recently approved agents and molecules in clinical trials.

Perchlozone Resistance in Clinical Isolates of Mycobacterium tuberculosis

The emergence of drug-resistant tuberculosis forced the development of new drugs and the screening of more effective or less toxic analogues. Mycolic acid biosynthesis is targeted by several antituberculosis drugs, isoniazid being one of the most important in tuberculosis therapy. Recently, perchlozone, acting on another step in the FAS-II cycle, was officially approved for tuberculosis treatment in the Russian Federation and was included in the Russian national clinical guidelines. Using the serial dilution method on 7H10 agar plates for perchlozone and a Sensititre MYCOTB microdilution plate, we analyzed the phenotypic properties of primary clinical isolates of M. tuberculosis and analyzed the molecular determinants of resistance to isoniazid, ethionamide, and perchlozone. We found a wide variation in the MIC of perchlozone from 2 to 64 mg/L, correlating with the overall resistance profile: the MIC was higher for MDR and pre-XDR isolates. The cross-resistance between ethionamide and perchlozone was driven by mutations in the ethA gene encoding monooxygenase responsible for the activation of both drugs. The presumably susceptible to perchlozone and wild-type strains had MICs ranging from 2 to 4 mg/L, and the breakpoint was estimated to be 4 or 8 mg/L. In conclusion, susceptibility to perchlozone is retained for a part of the MDR strains, as is susceptibility to ethionamide, providing the possibility of therapy for such cases based on phenotypic or molecular analysis.

In SilicoIdentification of Triclosan Derivatives as Potential Inhibitors of MutantMycobacterium tuberculosisInhA

Enoyl acyl carrier protein reductase (InhA) is a crucial enzyme for the biosynthesis of mycolic acids which are major compartments of the Mycobacterium tuberculosis (Mtb) cell wall. Direct inhibition of InhA without activation by drug-NADH adduct has clinical utility to overcome drug resistance. We aimed at the in silico identification of triclosan derivatives with the potential inhibitory effect of S94A-InhA as a clinically important mutant form. Caver Web 1.0 server was used to analyze the ligand transport through access tunnels. Two macrocyclic triclosan derivatives ( 4 and 6) could be identified with more energy-favorable transfer routes toward the enzyme active site. Molecular dynamics (MD) simulations (50 ns) of the best-scored compounds revealed the stability of enzyme structure upon binding to 4 and 6. Compound 4 could better retain enzyme stability upon target binding. Results of intermolecular H-bond analysis indicated that both complexes were mediated through hydrophobic contacts. Declined solvent accessible surface area (SASA) for the apo and bound enzyme states indicated non-destabilizing behavior and no structural relaxation. Electrostatic and van der Waals interactions between triclosan derivatives and their surroundings were used to acquire binding free energies through the linear interaction energy (LIE) method based on MD simulations (Average [Formula: see text], [Formula: see text] kcal/mol and [Formula: see text] kcal/mol). Both of the triclosan derivatives showed relatively stable energy variations and their steady accommodation inside enzyme active site could be confirmed during 50 ns. These results may be implicated in further structure-guided approaches against drug-resistant Mtb.

Computational evaluation of marine demospongiae sponges metabolites activity as mycolic acid biosynthesis inhibitors in Mycobacterium tuberculosis.

Mycobacterium tuberculosis is a bacterium that has historically had a substantial impact on human health. Despite advances in understanding and management of tuberculosis (TB), the disease remains a crucial problem that necessitates ongoing work to discover effective drugs, minimize transmission, and improve global health outcomes. The purpose of this study is to use molecular docking and absorption, distribution, metabolism, excretion, and toxicity (ADMET) analyses to explore the molecular interactions of different proteins that are involved in mycolic acid biosynthesis (HadAB, InhA, KasA, FabD, and beta-ketoacyl-acyl carrier protein synthase III) of M. tuberculosis with Demospongiae metabolites. The docking findings were evaluated using the glide gscore, and the top 10 compounds docked against each protein receptor were chosen. Furthermore, the selected compounds underwent ADMET analysis, indicating that they have the potential for therapeutic development. Among the selected compounds, makaluvamine G showed the highest binding affinity against HadAB, psammaplysin E showed highest binding affinity against InhA, pseudotheonamide D showed the highest binding affinity against KasA protein, dinordehydrobatzelladine B showed the highest binding affinity against FabD, and nagelamide X showed the highest binding affinity against beta-ketoacyl-acyl carrier protein synthase III. Additionally, molecular mechanics generalized born surface area (MM-GBSA) binding free energy and molecular dynamics simulations were used to support the docking investigations. The results of the study suggest that these compounds may eventually be used to treat TB. However, computer validations were included in this study, and more in vitro research is required to turn these prospective inhibitors into clinical drugs.