Antitubercular Isoniazid and Drug Resistance of Mycobacterium tuberculosis — A Review (original) (raw)
Related papers
Antimicrobial Agents and Chemotherapy, 2010
Mycobacterium tuberculosis enoyl-acyl-ACP reductase (InhA) has been demonstrated to be the primary target of isoniazid (INH). Recently, it was postulated that M. tuberculosis dihydrofolate reductase (DHFR) is also a target of INH, based on the findings that a 4R-INH-NADP adduct synthesized from INH by a nonenzymatic approach showed strong inhibition of DHFR in vitro , and overexpression of M. tuberculosis dfrA in M. smegmatis conferred a 2-fold increase of resistance to INH. In the present study, a plasmid expressing M. tuberculosis dfrA was transformed into M. smegmatis and M. tuberculosis strains, respectively. The transformant strains were tested for their resistance to INH. Compared to the wild-type strains, overexpression of dfrA in M. smegmatis and M. tuberculosis did not confer any resistance to INH based on the MIC values. Similar negative results were obtained with 14 other overexpressed proteins that have been proposed to bind some form of INH-NAD(P) adduct. An Escherichia...
Overview on mechanisms of isoniazid action and resistance in Mycobacterium tuberculosis
Infection, Genetics and Evolution, 2016
The tuberculosis (TB) is a disease caused by Mycobacterium tuberculosis (Mtb) and is considered a worldwide public health problem, classified as the leading cause of death by a single infectious agent. The conventional treatment is performed through the combination of drugs that exhibit precocious or sterilizing bactericidal activity. The commonly used drugs (knowing as first line drugs) are: izoniazide (INH), rifampicin (RIF), pyrazinamide (PZA) and ethambutol (ETH). However, the number of resistant TB cases (classified as RR-TB, MDR-TB and XDR-TB) to drugs has been growing in concern over the years. Of the total cases registered in 2016, about 600 thousand were resistant to one or more drugs used in the treatment. Resistance of Mtb strains to antituberculosis drugs is closely related to mutations in different bacillus genes. Multidrugresistant tuberculosis is a worldwide problem. A better understanding of the molecular mechanisms associated with the resistance to first-line drugs used in the TB treatment is of great importance for the development of new drugs, directly helping to reduce the number of resistant cases and bringing great benefits to public health. A review of the mechanisms of action of first-line drugs used in the treatment regimen to sensitive tuberculosis, as well as the main associated resistance mechanisms are.
Acetylation of isoniazid - a novel mechanism of isoniazid resistance in Mycobacterium tuberculosis
Isoniazid (INH), one of the first-line drugs used for the treatment of tuberculosis, is a pro-drug which is converted into its active form by the intracellular KatG enzyme of Mycobacterium tuberculosis. The activated drug hinders cell wall biosynthesis by inhibiting InhA protein. INH resistant strains of M. tuberculosis usually have mutations in katG, inhA, ahpC, kasA, and ndh genes. However, INH resistant strains which do not have mutations in any of these genes are reported, suggesting that these strains may adopt some other mechanism to become resistant to INH. In the present study we characterized Rv2170, a putative acetyltransferase in M. tuberculosis, to elucidate its role in inactivating isoniazid. The purified recombinant protein was able to catalyze transfer of acetyl group to INH from acetyl CoA. HPLC and LC-MS analyses showed that following acetylation by Rv2170, INH is broken down into isonicotinic acid and acetylhydrazine. Drug susceptibility assay and confocal analysis...
The Tuberculosis Prodrug Isoniazid Bound to Activating Peroxidases
Journal of Biological Chemistry, 2007
Isoniazid (INH, isonicotinic acid hydrazine) is one of only two therapeutic agents effective in treating tuberculosis. This prodrug is activated by the heme enzyme catalase peroxidase (KatG) endogenous to Mycobacterium tuberculosis but the mechanism of activation is poorly understood, in part because the binding interaction has not been properly established. The class I peroxidases ascorbate peroxidase (APX) and cytochrome c peroxidase (CcP) have active site structures very similar to KatG and are also capable of activating isoniazid. We report here the first crystal structures of complexes of isoniazid bound to APX and CcP. These are the first structures of isoniazid bound to any activating enzymes. The structures show that isoniazid binds close to the ␦-heme edge in both APX and CcP, although the precise binding orientation varies slightly in the two cases. A second binding site for INH is found in APX at the ␥-heme edge close to the established ascorbate binding site, indicating that the ␥-heme edge can also support the binding of aromatic substrates. We also show that in an active site mutant of soybean APX (W41A) INH can bind directly to the heme iron to become an inhibitor and in a different mode when the distal histidine is replaced by alanine (H42A). These structures provide the first unambiguous evidence for the location of the isoniazid binding site in the class I peroxidases and provide rationalization of isoniazid resistance in naturally occurring KatG mutant strains of M. tuberculosis.
In Silico Analysis Of Isoniazid Resistance In Mycobacterium Tuberculosis
2014
Altered drug binding may be an important factor in isoniazid (INH) resistance, rather than major changes in the enzyme's activity as a catalase or peroxidase (KatG). The identification of structural or functional defects in the mutant KatGs responsible for INH resistance remains as an area to be explored. In this connection, the differences in the binding affinity between wild-type (WT) and mutants of KatG were investigated, through the generation of three mutants of KatG, Ser315Thr [S315T], Ser315Asn [S315N], Ser315Arg [S315R] and a WT [S315]) with the help of software-MODELLER. The mutants were docked with INH using the software-GOLD. The affinity is lower for WT than mutant, suggesting the tight binding of INH with the mutant protein compared to WT type. These models provide the <em>in silico</em> evidence for the binding interaction of KatG with INH and implicate the basis for rationalization of INH resistance in naturally occurring KatG mutant strains of <em&...
The first-line specific antituberculous drug isoniazid inhibits the fatty acid elongation system (FAS) FAS-II involved in the biosynthesis of mycolic acids, which are major lipids of the mycobacterial envelope. The MabA protein that catalyzes the second step of the FAS-II elongation cycle is structurally and functionally related to the in vivo target of isoniazid, InhA, an NADH-dependent enoyl-acyl carrier protein reductase. The present work shows that the NADPH-dependent -ketoacyl reduction activity of MabA is efficiently inhibited by isoniazid in vitro by a mechanism similar to that by which isoniazid inhibits InhA activity. It involves the formation of a covalent adduct between MnIII-activated isoniazid and the MabA cofactor. Liquid chromatography- mass spectrometry analyses revealed that the isonicotinoyl-NADP adduct has multiple chemical forms in dynamic equilibrium. Both kinetic experiments with isolated forms and purification of the enzyme-ligand complex strongly suggested that the molecules active against MabA activity are the oxidized derivative and a major cyclic form. Spectrofluorimetry showed that the adduct binds to the MabA active site. Modeling of the MabA-adduct complex predicted an interaction between the isonicotinoyl moiety of the inhibitor and Tyr185. This hypothesis was supported by the fact that a higher 50% inhibitory concentration of the adduct was measured for MabA Y185L than for the wild-type enzyme, while both proteins presented similar affinities for NADP. The crystal structure of MabA Y185L that was solved showed that the substitution of Tyr185 induced no significant conformational change. The description of the first inhibitor of the -ketoacyl reduction step of fatty acid biosynthesis should help in the design of new antituberculous drugs efficient against multidrugresistant tubercle bacilli.
Journal of global antimicrobial resistance, 2017
In order to identify good leads based on isoniazid (INH) derivatives against INH resistance, which is one of the major contributors to the emergence of multidrug-resistant (MDR) that hampers the success of tuberculosis treatment. Mutations at codon 315 in the katG gene coding for catalase-peroxidase (KatG) is the major cause for INH resistance in Mycobacterium tuberculosis(MTB). The most prevalent mutation at this codon is Ser to Thr substitution (S315T). The other substitutions include S315I, S315R, S315N and S315G. In this study, all the 5 (S315T, S315I, S315R, S315N and S315G) mutants (MTs) were docked and simulated with 50 derivatives of INH in comparison to the wild type (WT-S315). The docking results suggest that compounds (C)-30, 45 and 50, gave the highest scores when bound to the MTs of KatG. Of note, the C-50 produced high score with the WT as well three MTs (S315T, S315I, and S315R). Simulation studies indicate that of the three compounds, C-50 exhibited minimal deviation...
Gene, 2018
Mycobacterium tuberculosis katG gene is responsible for production of an enzyme catalase peroxidase that peroxidises and activates the prodrug Isoniazid (INH), a first-line antitubercular agent. INH interacts with catalase peroxidase enzyme within its heme pocket and gets converted to an active form. Mutations occurring in katG gene are often linked to reduced conversion rates for INH. This study is focussed on one such mutation occurring at residue 279, where glycine often mutates to aspartic acid (G279D). In the present study, several structural analyses were performed to study the effect of this mutation on functionality of KatG protein. On comparison, mutant protein exhibited a lower docking score, smaller binding cavity and reduced affinity towards INH. Molecular dynamics analysis revealed the mutant to be more rigid and less compact than the native protein. Essential dynamics analysis determined correlated motions of residues within the protein structure. G279D mutant was foun...
Chemical disarming of isoniazid resistance in Mycobacterium tuberculosis
Proceedings of the National Academy of Sciences, 2019
Mycobacterium tuberculosis ( Mtb ) killed more people in 2017 than any other single infectious agent. This dangerous pathogen is able to withstand stresses imposed by the immune system and tolerate exposure to antibiotics, resulting in persistent infection. The global tuberculosis (TB) epidemic has been exacerbated by the emergence of mutant strains of Mtb that are resistant to frontline antibiotics. Thus, both phenotypic drug tolerance and genetic drug resistance are major obstacles to successful TB therapy. Using a chemical approach to identify compounds that block stress and drug tolerance, as opposed to traditional screens for compounds that kill Mtb , we identified a small molecule, C10, that blocks tolerance to oxidative stress, acid stress, and the frontline antibiotic isoniazid (INH). In addition, we found that C10 prevents the selection for INH-resistant mutants and restores INH sensitivity in otherwise INH-resistant Mtb strains harboring mutations in the katG gene, which e...
Protein Science, 2005
Isoniazid is a frontline drug used in the treatment of tuberculosis (TB). Isoniazid is a prodrug, requiring activation in the mycobacterial cell by the catalase/peroxidase activity of the katG gene product. TB kills two million people every year and the situation is getting worse due to the increase in prevalence of HIV/AIDS and emergence of multidrug-resistant strains of TB. Arylamine N-acetyltransferase (NAT) is a drug-metabolizing enzyme (E.C. 2.1.3.5). NAT can acetylate isoniazid, transferring an acetyl group from acetyl coenzyme A onto the terminal nitrogen of the drug, which in its N-acetylated form is therapeutically inactive. The bacterium responsible for TB, Mycobacterium tuberculosis, contains and expresses the gene encoding the NAT protein. Isoniazid binds to the NAT protein from Salmonella typhimurium and we report here the mode of binding of isoniazid in the NAT enzyme from Mycobacterium smegmatis, closely related to the M. tuberculosis and S. typhimurium NAT enzymes. The mode of binding of isoniazid to M. smegmatis NAT has been determined using data collected from two distinct crystal forms. We can say with confidence that the observed mode of binding of isoniazid is not an artifact of the crystallization conditions used. The NAT enzyme is active in mycobacterial cells and we propose that isoniazid binds to the NAT enzyme in these cells. NAT activity in M. tuberculosis is likely therefore to modulate the degree of activation of isoniazid by other enzymes within the mycobacterial cell. The structure of NAT with isoniazid bound will facilitate rational drug design for anti-tubercular therapy.