Evolutionary genomics analysis reveals gene expansion and functional diversity of arylalkylamine N-acetyltransferases in the Culicinae subfamily of mosquitoes

Arylalkylamine N-acetyltransferase(aaNAT),considered a potential new insecticide target,catalyzes the acetylation of arylalkylamine substrates such as serotonin and dopamine and,hence,mediates diverse functions in insects.However,the origin of insect aaNATs(iaaNATs)and the evolutionary process that generates multiple aaNATs in mosquitoes remain largely unknown.Here,we have analyzed the genomes of 33 species to explore and expand our understanding of the molecular evolution of this gene family in detail.We show that aaNAT orthologs are present in Bacteria,Cephalochordata,Chondrichthyes,Cnidaria,Crustacea,Mammalia,Placozoa,and Teleoste,as well as those from a number of insects,but are absent in some species of Annelida,Echinozoa,and Mollusca as well as Arachnida.Particularly,more than 10 aaNATs were detected in the Culicinae subfamily of mosquitoes.Molecular evolutionary analysis of aaNAT/aaNAT-like genes in mosquitoes reveals that tandem duplication events led to gene expansion in the Culicinae subfamily of mosquitoes more than 190 million years ago.Further selection analysis demonstrates that mosquito aaNATs evolved under strongly positive pressures that generated functional diversity following gene duplication events.Overall,this study may provide novel insights into the molecular evolution of the aaNAT family in mosquitoes.

Polymorphism of N-acetyltransferase 2 (NAT2) Gene Polymorphism in Shanghai population: Occupational and Non-occupational Bladder Cancer Patient Groups

Objective Arylamine N-acetyltransferases (NATs) are involved in the detoxification of aromatic amines and hydrazine. In order to explore the possible association of NAT2 polymorphism with bladder cancer risk in benzidine exposed or non-exposed Chinese individuals, healthy subjects, subjects with bladder cancer of a former benzidine exposed cohort in Shanghai dyestuff industry and a group of bladder cancer patients without known occupational exposure to aromatic amines were genotyped for NAT2 gene polymorphism. Methods NAT2 genotyping was performed with a set of RFLP procedures at seven major polymorphic loci of gene coding area: G191A, C282T, T341C, C481T, G590A, A803G and G857A. Results The wild allele NAT2 *4 was the most prevalent allele (59%) in healthy individuals. The alleles NAT2*6A and NAT2*7B were also frequently observed (21% and 17%, respectively). In contrast to Caucasians, the percentage of slow acetylators was lower (12% in Chinese vs. 58% in Caucasians, P<0.001). No relevant differences were observed for homogenous rapid, heterogeneous rapid/slow and homogeneous slow acetylation genotypes between the healthy subjects and both groups of bladder cancer patients. Conclusion The present work did not support the association of slow acetylating genotypes of NAT2 gene with elevated risk of bladder cancer in Chinese whereas it was documented as an important genetically determined risk factor in Caucasians. Different mechanisms might play a role in individual susceptibility to bladder cancer related with aromatic amine exposure in various races or ethnic groups.

N-Acetyltransferase 2 genetic polymorphisms and risk of colorectal cancer

AIM:To investigate the possible association between meat intake,cigarette smoking and N-acetyltransferase 2 (NAT2) genetic polymorphisms on colorectal cancer (CRC) risk.METHODS:Patients with CRC were matched for gender and age to healthy controls.Meat intake and cigarette smoking were assessed using a specific frequency questionnaire.DNA was extracted from peripheral blood and the genotypes of the polymorphism were assessed by polymerase chain reaction-restriction fragment length polymorphism.Five NAT2 alleles were studied (WT,M1,M2,M3 and M4) using specific digestion enzymes.RESULTS:A total of 147 patients with colorectal cancer (76 women and 90 men with colon cancer) and 212 controls were studied.The mean age of the two groups was 62 years.More than half the subjects (59.8% in the case group and 51.9% in the control group) were NAT2 slow acetylators.The odds ratio for colorectal cancer was 1.38 (95% CI:0.90-2.12) in slow acetylators.Although the number of women was small (n=76 in the case group),the cancer risk was found to be lower in intermediate (W/Mx) acetylators [odds ratio (OR):0.55,95% confidence interval (95% CI):0.29-1.02].This difference was not observed in men (OR:0.56,95% CI:0.16-2.00).Among NAT2 fast acetylators (W/W or W/Mx),meat consumption more than 3 times a week increased the risk of colorectal cancer (OR:2.05,95% CI:1.01-4.16).In contrast,cigarette smoking increased the risk of CRC among slow acetylators (OR:1.97,95% CI:1.02-3.79).CONCLUSION:The risk of CRC was higher among fast acetylators who reported a higher meat intake.Slow NAT2 acetylation was associated with an increased risk of CRC.

Crohn's disease in Japanese is associated with a SNP-haplotype of N-acetyltransferase 2 gene

AIM： To investigate the frequency and distribution of /V-acetyltransferase 2 （NAT2） and uridine 5＇-diphosphate （UDP）-glucuronosyltransferase 1A7 （UGT1A7） genes in patients with ulcerative colitis （UC） and Crohn＇s disease （CD）. METHODS： Frequencies and distributions of IVAT2 and UGT1A7SNPs as well as their haplotypes were investigated in 95 patients with UC, 60 patients with CD, and 200 gender-matched, unrelated, healthy, control volunteers by PCR-restriction fragment length polymorphism （RFLP）, PCR-denaturing high-performance liquid chromatography （DHPLC）, and direct DNA sequencing. RESULTS： Multiple logistic regression analysis revealed that the frequency of haplotype, NAT2＊7B, significantly increased in CD patients, compared to that in controls （P= 0.0130, OR = 2.802, 95%CI = 1.243-6.316）. However, there was no association between NAT2 haplotypes and UC, or between any UGT1A7haplotypes and inflammatory bowel disease （IBD）. CONCLUSION： It is likely that the NAT2 gene is one ofthe determinants for CD in Japanese. Alternatively, a new CD determinant may exist in the 8p22 region, where NAT2 is located.

Are polymorphisms of N-acetyltransferase genes susceptible to primary liver cancer in Luoyang, China?

AIM: To identify whether the polymorphisms of the Nacetyltransferase (NAT) genes are susceptible to primary liver cancer (PLC) in Luoyang, a PLC low-incidence area of China.METHODS: The NAT1 and NAT2 genotypes of 96 PLC cases and 173 controls were determined by PCR-RFLP.Both interaction between NAT1 or NAT2 and environmental risk factors were analyzed based on case control study.RESULTS: Compared to the control group, the frequencies of alleles NAT1*3, NAT1*4, NAT1*10, NAT1*14B and alleles NAT2*4, NAT2*6, NAT2*7 in PLC group showed no statistically significant difference (x2 = 2.61 and 4.16,respectively, both P＞0.05). The frequencies of NAT1 genotypes NAT1*3/*3, NAT1*3/*4, NAT1*3/*10,NAT1*3/*14B, NAT1*4/*4, NAT1*4/*10, NAT1*4/*14B,NAT1*10/*10, NAT1*10/*14B, and NAT2 genotypes NAT2*4/*4, NAT2*4/*6, NAT2*4/*7, NAT2*6/*6,NAT2*6/*7 and NAT2*7/*7 also had no statistically significant difference between the two groups (x2 = 11.86 and 2.94respectively both, P＞0.05). Neither the frequencies of rapid and slow NAT1 acetylators nor the frequencies of rapid and slow NAT2 acetylators were significantly different between the two groups (x2 = 0.598 and 0.44,respectively, both P＞0.05). The interaction betweenNAT1*10 and occupational exposures was found significant with an odds ratio of 3.40 (x2 = 8.42, P = 0.004,OR 95%CI:1.03-11.22). But no interaction was found between NAT2 and any environmental risk factors.CONCLUSION: The polymorphisms of NAT1 and NAT2are not susceptible to PLC in Luoyang. Allele NAT1*10interacts with occupational exposures.

Inflammatory cytokines suppress arylamine N-acetyltransferase 1 in cholangiocarcinoma cells

AIM： To evaluate the effect of inflammatory cytokines on arylamine N-acetyltransferase 1 （NAT1）, which is a phase-U enzyme involved in the biotransformation of aromatic and heterocyclic amines found in food, drugs and the environment. METHODS： Human cholangiocarcinoma KKU-100 cells were treated with a mixture of proinflammatory cytokines （interferon-7, interleukin-l and tumor necrosis factor-m） for 48 h, and the effect on NAT1 activity was assessed by high performance liquid chromatography, while NAT1 expression was determined by reverse-transcription polymerase chain reaction. The oxidative stress on the cells was examined by the formation of nitric oxide, superoxide anion and glutathione （GSH） levels. The cells were also treated with S-nitroso-glutathione （GSNO）, a nitric oxide donor, to see if the responses were similar to those obtained with the inflammatory cytokines. RESULTS： Cytokines suppressed NAT1 activity, reducing the Vmax without affecting the Am. Cytokines also had a significant impact on the induction of nitric oxide production and in reducing the redox ratios of glutathione （GSH） and GSH disulfide. Treatment with GSNO for 2-48 h reduced NAT1 activity without affecting the GSH ratio. Moreover, inflammatory cytokines and GSNO suppressed NAT1 mRNA expression. CONCLUSION： These findings indicate an association between inflammation and suppression of NAT1, which perhaps contributes to chemical-mediated toxicity and carcinogenesis,

Density Functional Theory Study on the Histidine-assisted Mechanism of Arylamine N-Acetyltransferase Acetylation

Arylamine N-acetyltransferases （NATs, EC 2.3.1.5） catalyze the N-acetylation of primary arylamines, and play a key role in the biotransformation and metabolism of drugs, carcinogens, etc. In this paper, three possible reaction mechanisms are investigated and the results indicate that if the acetyl group directly transfers from the donor to the acceptor, the high activation energies will make it hard to obtain the target products. When using histidine to mediate the acetylation process, these energies will drop in the 15-45 kJ/mol range. If the histidine residue is protonated, the corresponding energies will be decreased by about 35-87 kJ/mol. The calculations predict an enzymatic acetylation mechanism that undergoes a thiolate-imidazolium pair, which agrees with the experimental results very well.

N-acetyltransferase 2: Slow, intermediate or fast? A booming question of the molecular epidemiology in cancer research

Throughout history, humanity has referred to reactions occurring with food, plants and, recently, medicines or drugs. The increase in pulmonary tuberculosis cases and the availability of treatment showed that genetic human differences can interfere in the capacity to metabolize drugs. There are remarkable genetic polymorphisms of N-acetyltransferase 2 (NAT2) activity that have been associated with different levels of susceptibility to developing many kinds of cancers. This review considers the field as an open window for the application of molecular epidemiology tools that led to the development of pharmacogenomics. We cover historical data and the most recent knowledge about NAT2 genetic polymorphisms and its distribution in different populations, which is an important concept being incorporated in epidemiological studies of cancer risk. We present up to date information about these studies, including meta-analysis based on the NAT2 distribution in different types of cancer. A critical broad at advances in NAT2 research, high-lighting recent studies related to NAT2 alleles in cancer susceptibility. Although there are multifactorial aspects involved in cancer risk, the variability in NAT2 allelic frequency can be related to carcinogenesis through alterations in the metabolic rate after exposure to carcinogens.

Night-time Rise in Rat Pineal N-Acetyltransferase due to Carbaryl Administration Is Reduced by Propranolol Treatment

The purpose of the present study was to examine the effects of administration of sublethal doses of carbaryl on nighttime rat pineal melatonin synthesis in the presence and absence of propranolol, a β-adrenergic receptor antagonist. Two groups of adult male albino rats were administered orally N-methyl-l-naphthylcarbamate (carbaryl) (8. 33mg/kg BW daily in corn oil) for six successive days; another two groups received corn oil only.On the last day of carbaryl treatment, half of the animals received an intraperitoneal injection of propranolol (20 mg/kg body weight, one hour before lights off). The other two groups were given a saline injection. Four hours after darkness onset, pineal N-acetyltransferase (NAT) and hydroxyindole-O-methyltransferase (HIOMT) activities as well as pineal concentrations of 5-hydroxytryptophan (5HTP), serotonin (5HT),5-hydroxyindole acetic acid (5HIAA) and pineal and serum melatonin levels were measured. Nocturnal NAT activity was increased due to carbaryl administration but the pesticide was ineffective in stimulating NAT activity in rats treated with propranolol.Pineal 5HT was decreased due to carbaryl administration but 5HTP and 5HIAA levels were unaffected. Pineal and serum melatonin levels were decreased due to propranolol treatment. The results indicate that carbaryl may influence pineal NAT activity by a mechanism that involves β-adrenergic neural transmission.

N-乙酰基转移酶2(NAT2)基因多态性与肺癌易感性关系的Meta分析

目的探讨分析NAT2多态性与肺癌易感性的关系。方法在中英文数据库中按照统一的检索策略,全面检索至2013年8月1日有关NAT2多态性与肺癌风险关系的观察性研究相关文献。按照纳入与排除标准选择文献、提取资料和评价质量进行Meta分析。结果共纳入23篇文献,分别来自15个国家,累计肺癌病例4 425人,对照病例6 663人。结论本Meta分析结果表明:NAT2基因多态性与肺癌易感性之间未见显著关联。

Relationship between metabolic enzyme polymorphism and colorectal cancer

AIM: To clarify the influence of genetic polymorphisms on colorectal cancer. METHODS: The results of 42 related studies from 1990 to 2001 were analyzed by meta-analysis. Mantel-Haenzel fixed-effect model or Dersimonian-Laird random-effect model and ReviewManager 4.1 statistical program were applied in processing the data. RESULTS: Meta analysis of these studies showed that GSTT1 deletion (pooled OR= 1.42), N-acetyltransferase 2 (NAT2)-rapid acetylator phenotype and genotye (pooled OR = 1.08) and NAT2-rapid acetylator phenotype (pooled OR = 1.15) had a significantly increased risk for colorectal cancer (P<0.05), other genotypes like GSTM1 deletion, GSTP1 1le105Val, NAT1*10, NAT2-rapid acetylator genotype CYP1A1 Lle462Val, CYP1A1 MspI*C, MTHFR C677T and MTR A2759G had no significant relationship with colorectal cancer (P>0.05). CONCLUSION: Risks for colorectal cancer are significantly associated with the genetic polymorphisms of GSTT1 deletion, NAT2-rapid acetylator phenotype and genotye and NAT2-rapid acetylator phenotype.

Frequent loss of heterozygosity at 8p22 chromosomal region in diffuse type of gastric cancer

AIM: To study the loss of heterozygosity (LOH) at 8p21-23 locus in diffuse gastric cancer.METHODS: To evaluate the involvement of this region in gastric cancer, we used eight microsatellite markers covering two Mb of mentioned region, to perform a high-resolution analysis of allele loss in 42 cases of late diffuse gastric adenocarcinoma.RESULTS: Six of these STS makers: D8S1149, D8S1645, D8S1643, D8S1508, D8S1591, and D8S1145 showed 36%, 28%, 37%, 41%, 44% and 53% LOH, respectively.CONCLUSION: A critical region of loss, close to the NAT2 locus and relatively far from FEZ1 gene currently postulated as tumor suppressor gene in this region.

Trimethoprim-Sulfamethoxazole-Induced Hepatitis in Mixed Connective Tissue Disease

Trimethoprim-Sulfamethoxazole (TMP-SMZ) is associated with severe hepatic toxicity or liver failure. We present a case of severe hepatic toxicity for whom TMP-SMZ was prescribed as part of treatment for mixed connective tissue disease (MCTD). TMP-SMZ was used to prevent complications from steroid therapy, but fever and hepatic toxicity developed with repeated TMP-SMZ medication. While the drug lymphocyte stimulation test (DLST) for TMP-SMZ showed negative, the genotype for N-acetyltransferase 2 (NAT2) showed type *6/*7, which is the slow acetylating type for NAT2 activity. This finding for NAT2 genotype and the patient’s clinical history lead us to speculate that her fever and hepatic toxicity were caused by TMP-SMZ.

Molecular Docking and ADMET Study of Emodin Derivatives as Anticancer Inhibitors of NAT2, COX2 and TOP1 Enzymes

Over the past years natural products and/or their derivatives have continued to provide cancer chemotherapeutics. Glycosides derivatives of emodin are known to possess anticancer activities. An in silico study was carried out to evaluate emodin derivatives as inhibitors of Arylamine N-Acetyltransferase 2, Cyclooxygenase 2 and Topoisomerase 1 enzymes, predict their pharmacokinetics and explore their bonding modes. Molecular docking study suggested that D2, D5, D6 and D9 to be potent inhibitors of NAT2, while D8 was suggested to be a potent inhibitor of TOP1. Derivatives D2, D5, D6 and D9 bind to the same pocket with different binding conformation. Pharmacokinetic study suggested that selected emodin derivatives can be potential cancer chemotherapeutic agent. Physicochemical parameters such density, balaban index, surface tension, logP and molar reflectance correlated to compounds activity. These finding provides a potential strategy towards developing NAT2 and TOP1 inhibitors.

Adverse Events Clustering with NAT2 Slow Metabolisers following Deparasitization in Children in Bangolan, NWR Cameroon

Inter individual differences in the metabolism of antimalarials could be due to polymorphism of NAT2 gene. The authors determined the genotypic frequencies of single nucleotide polymorphism （SNP） of NAT2 gene and it＇s implication in antimalarial treatment during a vitamin A and zinc supplementation intervention in children aged 6 to 24 months. Children were deparasitized with artesunate-amodiaquine （ASAQ）-toddler 50/135 mg. Pharmacovigilance was done for 40 days, adverse events recorded and blood was spotted on filter paper for DNA extraction by chelex method. PCR-RFLP was performed with restriction enzymes KpnI, TaqI, and BamHl for detection of SNPs of NAT2. Allelic frequencies and phenotypes were compared between participants with or without adverse drug events. The prevalence of fast, slow and intermediate acetylators was 55%, 30% and 11% respectively. There was a significant association （P = 0.035） between NAT2 slow acetylators （and susceptibility to develop skin rash. No significant difference was observed between fast and slow acetylators and susceptibility to develop fever, anorexia, cough and common cold. Slow acetylators were more susceptible, （P = 0.011） to develop any adverse event The NAT2 slow acetylator phenotype was the most predominant and individuals with this phenotype were more significantly susceptible to develop adverse events to ASAQ.

NAT10-mediated ac 4 C-modified ANKZF1 promotes tumor progression and lymphangiogenesis in clear-cell renal cell carcinoma by attenuating YWHAE-driven cytoplasmic retention of YAP1

Background:Lymphatic metastasis is one of the most common metastatic routes and indicates a poor prognosis in clear-cell renal cell carcinoma(ccRCC).N-acetyltransferase 10(NAT10)is known to catalyze N4-acetylcytidine(ac4C)modification of mRNA and participate in many cellular processes.However,its role in the lymphangiogenic process of ccRCC has not been reported.This study aimed to elucidate the role of NAT10 in ccRCC lymphangiogenesis,providing valuable insights into potential therapeutic targets for intervention.Methods:ac4C modification and NAT10 expression levels in ccRCC were assessed using public databases and clinical samples.Functional investigations involved manipulating NAT10 expression in cellular and mouse models to study its role in ccRCC.Mechanistic insights were gained through a combination of RNA sequencing,mass spectrometry,co-immunoprecipitation,RNA immuno-precipitation,immunofluorescence,and site-specific mutation analyses.Results:We found that ac4C modification and NAT10 expression levels increased in ccRCC.NAT10 promoted tumor progression and lymphangiogene-sis of ccRCC by enhancing the nuclear import of Yes1-associated transcriptional regulator(YAP1).Subsequently,we identified ankyrin repeat and zinc fin-ger peptidyl tRNA hydrolase 1(ANKZF1)as the functional target of NAT10,and its upregulation in ccRCC was caused by NAT10-mediated ac4C modifi-cation.Mechanistic analyses demonstrated that ANKZF1 interacted with tyro-sine 3-monooxygenase/tryptophan 5-monooxygenase activation protein epsilon(YWHAE)to competitively inhibit cytoplasmic retention of YAP1,leading to transcriptional activation of pro-lymphangiogenic factors.Conclusions:These results suggested a pro-cancer role of NAT10-mediated acetylation in ccRCC and identified the NAT10/ANKZF1/YAP1 axis as an under-reported pathway involving tumor progression and lymphangiogenesis in ccRCC.

A pilot study of the modulation of sirtuins on arylamine N-acetyltransferase 1 and 2 enzymatic activity

Arylamine N-acetyltransferase(NAT; E.C. 2.3.1.5) enzymes are responsible for the biotransformation of several arylamine and hydrazine drugs by acetylation. In this process, the acetyl group transferred to the acceptor substrate produces NAT deacetylation and, in consequence, it is susceptible of degradation. Sirtuins are protein deacetylases, dependent on nicotine adenine dinucleotide,which perform post-translational modifications on cytosolic proteins. To explore possible sirtuin participation in the enzymatic activity of arylamine NATs, the expression levels of NAT1, NAT2,SIRT1 and SIRT6 in peripheral blood mononuclear cells(PBMC) from healthy subjects were examined by flow cytometry and Western blot. The in situ activity of the sirtuins on NAT enzymatic activity was analyzed by HPLC, in the presence or absence of an agonist(resveratrol) and inhibitor(nicotinamide) of sirtuins. We detected a higher percentage of positive cells for NAT2 in comparison with NAT1, and higher numbers of SIRT1t cells compared to SIRT6 in lymphocytes. In situ NAT2 activity in the presence of NAM inhibitors was higher than in the presence of its substrate, but not in the presence ofresveratrol. In contrast, the activity of NAT1 was not affected by sirtuins. These results showed that NAT2 activity might be modified by sirtuins.

N-acetyltransferase 10 promotes colon cancer progression by inhibiting ferroptosis through N4-acetylation and stabilization of ferroptosis suppressor protein 1 (FSP1) mRNA

Background:N-acetyltransferase 10(NAT10)is the only enzyme known tomediate the N4-acetylcytidine(ac4C)modification of mRNA and is crucial formRNA stability and translation efficiency.However,its role in cancer development and prognosis has not yet been explored.This study aimed to examine the possible role of NAT10 in colon cancer.Methods:The expression levels ofNAT10were evaluated by immunohistochemical analyses with a colon cancer tissue microarray,and its prognostic value in patients was further analyzed.Quantitative real-time polymerase chain reaction(qRT-PCR)and Western blotting were performed to analyze NAT10 expression in harvested colon cancer tissues and cell lines.Stable NAT10-knockdown and NAT10-overexpressing colon cancer cell lines were constructed using lentivirus.The biological functions of NAT10 in colon cancer cell lines were analyzed in vitro by Cell Counting Kit-8(CCK-8),wound healing,Transwell,cell cycle,and ferroptosis assays.Xenograft models were used to analyze the effect of NAT10 on the tumorigenesis and metastasis of colon cancer cells in vivo.Dot blotting,acetylated RNA immunoprecipitation-qPCR,and RNA stability analyses were performed to explore the mechanism by which NAT10 functions in colon cancer progression.Results:NAT10 was upregulated in colon cancer tissues and various colon cancer cell lines.This increased NAT10 expression was associated with shorter patient survival.Knockdown of NAT10 in two colon cancer cell lines(HT-29 and LoVo)impaired the proliferation,migration,invasion,tumor formation and metastasis of these cells,whereas overexpression of NAT10 promoted these abilities.Further analysis revealed that NAT10 exerted a strong effect on the mRNA stability and expression of ferroptosis suppressor protein 1(FSP1)in HT-29 and LoVo cells.In these cells,FSP1 mRNA was found to be modified by ac4C acetylation,and this epigenetic modification was associated with the inhibition of ferroptosis.Conclusions:Our study revealed that NAT10 plays a critical role in colon cancer development by affecting FSP1 mRNA stability and ferroptosis,suggesting that NAT10 could be a novel prognostic and therapeutic target in colon cancer.

Arylamine N-acetyltransferase 2 genotype-dependent N-acetylation of isoniazid in cryopreserved human hepatocytes

Cryopreserved human hepatocytes were used to investigate the role of arylamine N-acetyltransferase 2 (NAT2; EC 2.3.1.5) polymorphism on the N-acetylation of isoniazid (INH). NAT2 genotype was determined by Taqman allelic discrimination assay and INH N-acetylation was measured by high performance liquid chromatography. INH N-acetylation rates in vitro exhibited a robust and highly significant (P<0.005) NAT2 phenotype-dependent metabolism. N-acetylation rates in situ were INH concentration- and time-dependent. Following incubation for 24 h with 12.5 or 100 µmol/L INH, acetyl-INH concentrations varied significantly (P = 0.0023 and P = 0.0002) across cryopreserved human hepatocytes samples from rapid, intermediate, and slow acetylators, respectively. The clear association between NAT2 genotype and phenotype supports use of NAT2 genotype to guide INH dosing strategies in the treatment and prevention of tuberculosis.

Identification of arylamine N-acetyltransferase inhibitors as an approach towards novel anti-tuberculars

New anti-tubercular drugs and drug targets are urgently needed to reduce the time for treatment and also to identify agents that will be effective against Mycobacterium tuberculosis persisting intracellularly.Mycobacteria have a unique cell wall.Deletion of the gene for arylamine N-acetyltransferase(NAT)decreases mycobacterial cell wall lipids,particularly the distinctive mycolates,and also increases antibiotic susceptibility and killing within macrophage of Mycobacterium bovis BCG.The nat gene and its associated gene cluster are almost identical in sequence in M.bovis BCG and M.tuberculosis.The gene cluster is essential for intracellular survival of mycobacteria.We have therefore used pure NAT protein for high-throughput screening to identify several classes of small molecules that inhibit NAT activity.Here,we characterize one class of such molecules—triazoles—in relation to its effects on the target enzyme and on both M.bovis BCG and M.tuberculosis.The most potent triazole mimics the effects of deletion of the nat gene on growth,lipid disruption and intracellular survival.We also present the structure-activity relationship between NAT inhibition and effects on mycobacterial growth,and use ligand-protein analysis to give further insight into the structure-activity relationships.We conclude that screening a chemical library with NAT protein yields compounds that have high potential as anti-tubercular agents and that the inhibitors will allow further exploration of the biochemical pathway in which NAT is involved.