Publications by authors named "Johayra Simithy"

17 Publications

  • Page 1 of 1

Barriers to lung cancer referral, diagnosis, and treatment in Central America and the Caribbean: the health professionals' perspectives.

Support Care Cancer 2021 Feb 26;29(2):751-757. Epub 2020 May 26.

Personalized Healthcare, Genentech, South San Francisco, CA, 94080, USA.

Purpose: To identify the perspectives from healthcare providers about the limitations in referral, diagnosis, and treatment of lung cancer (LC) patients.

Methods: A cross-sectional study through an Internet-based survey was addressed to physicians of multidisciplinary teams in charge of LC patients from Cuba, Curacao, Costa Rica, Dominican Republic, El Salvador, Guatemala, Honduras, Jamaica, Panama, and Trinidad and Tobago. The questions focused on physicians' perspectives concerning waiting times and the availability of diagnostic and staging procedures in their settings, as well as the access to systemic therapies and continuous medical education (CME).

Results: A total of 152 physicians responded to the online questionnaire (response rate 24.9%). Delays in biopsy results were the main barrier for LC diagnosis as identified by 48.2% of the respondents, followed by patients not being referred in time (31.3%), delays for staging procedures (11.4%), and time taken for biopsy (9%). Almost one-half of physicians perceived that patients are diagnosed in advanced stages. A total of 29 respondent physicians (19.1%) reported limited access to immunohistochemical or genetic analysis for common mutations. Although 73 physicians (48.0%) confirmed that their centers provided radiotherapy and systemic therapy for their patients, immunotherapy was not available in the institutions of 30 physicians (19.7%). A total of 42 practitioners (27.6%) reported that they did not have access to CME on LC topics due to working or budget restrictions.

Conclusions: This study revealed among respondents the main barriers for an appropriate management of LC patients in the Central American and Caribbean Region. Further studies must validate these findings.
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http://dx.doi.org/10.1007/s00520-020-05532-8DOI Listing
February 2021

Near infrared (NIR)-spectroscopy and in-vitro dissolution absorption system 2 (IDAS2) can help detect changes in the quality of generic drugs.

Drug Dev Ind Pharm 2020 Jan 8;46(1):80-90. Epub 2020 Jan 8.

Absorption Systems Panama, Inc, Panama City, Panama.

While Health authorities in Panama strive to increase generic drug use to contain the rising costs of medicines, there is still hesitation to embrace generic drugs. Thus, regulators and drug companies need to ensure the quality, safety and efficacy of generic drugs. One prevailing concern is the absence of control over lot-to-lot changes, which may impact consistent therapeutic performance. The objective of this work was to determine whether near-infrared spectroscopy (NIR) could detect product changes. Calibration models were built using reference (standard) tablets of two products: Virax (200 mg acyclovir) and Amlopin (5 mg amlodipine). Then, to assess the sensitivity of NIR to product changes we compared reference versus deliberately-modified formulations of these products. Comparisons were made using principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA) of NIR spectra. Several modified lots were different from reference lots, and 3D score plots showed greater discrimination by PLS-DA than PCA. The Kth nearest neighbor scores (KNN) of the modified batches were used to classify formulations as identical or not identical versus the reference. In addition, the differences detected by NIR were correlated with different dissolution and/or permeation in the dissolution absorption system 2 (IDAS2): NIR and IDAS2 yielded the same rank-order of difference for the modified lots tested. This study suggests that NIR and IDAS2 can help detect lots of generic drugs that differ from the reference lots. This strategy may help regulatory agencies in developing countries to safeguard patients against lot-to-lot changes in generic products.
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http://dx.doi.org/10.1080/03639045.2019.1701004DOI Listing
January 2020

Targeting CDK9 Reactivates Epigenetically Silenced Genes in Cancer.

Cell 2018 11 25;175(5):1244-1258.e26. Epub 2018 Oct 25.

The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, MD 21231, USA.

Cyclin-dependent kinase 9 (CDK9) promotes transcriptional elongation through RNAPII pause release. We now report that CDK9 is also essential for maintaining gene silencing at heterochromatic loci. Through a live cell drug screen with genetic confirmation, we discovered that CDK9 inhibition reactivates epigenetically silenced genes in cancer, leading to restored tumor suppressor gene expression, cell differentiation, and activation of endogenous retrovirus genes. CDK9 inhibition dephosphorylates the SWI/SNF protein BRG1, which contributes to gene reactivation. By optimization through gene expression, we developed a highly selective CDK9 inhibitor (MC180295, IC50 = 5 nM) that has broad anti-cancer activity in vitro and is effective in in vivo cancer models. Additionally, CDK9 inhibition sensitizes to the immune checkpoint inhibitor α-PD-1 in vivo, making it an excellent target for epigenetic therapy of cancer.
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http://dx.doi.org/10.1016/j.cell.2018.09.051DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6247954PMC
November 2018

Slow-Binding Inhibition of Mycobacterium tuberculosis Shikimate Kinase by Manzamine Alkaloids.

Biochemistry 2018 08 31;57(32):4923-4933. Epub 2018 Jul 31.

Department of Drug Discovery and Development, Harrison School of Pharmacy , Auburn University , 4306 Walker Building , Auburn , Alabama 36849 , United States.

Tuberculosis represents a significant public health crisis. There is an urgent need for novel molecular scaffolds against this pathogen. We screened a small library of marine-derived compounds against shikimate kinase from Mycobacterium tuberculosis ( MtSK), a promising target for antitubercular drug development. Six manzamines previously shown to be active against M. tuberculosis were characterized as MtSK inhibitors: manzamine A (1), 8-hydroxymanzamine A (2), manzamine E (3), manzamine F (4), 6-deoxymanzamine X (5), and 6-cyclohexamidomanzamine A (6). All six showed mixed noncompetitive inhibition of MtSK. The lowest K values were obtained for 6 across all MtSK-substrate complexes. Time-dependent analyses revealed two-step, slow-binding inhibition. The behavior of 1 was typical; initial formation of an enzyme-inhibitor complex (EI) obeyed an apparent K of ∼30 μM with forward ( k) and reverse ( k) rate constants for isomerization to an EI* complex of 0.18 and 0.08 min, respectively. In contrast, 6 showed a lower K for the initial encounter complex (∼1.5 μM), substantially faster isomerization to EI* ( k = 0.91 min), and slower back conversion of EI* to EI ( k = 0.04 min). Thus, the overall inhibition constants, K*, for 1 and 6 were 10 and 0.06 μM, respectively. These findings were consistent with docking predictions of a favorable binding mode and a second, less tightly bound pose for 6 at MtSK. Our results suggest that manzamines, in particular 6, constitute a new scaffold from which drug candidates with novel mechanisms of action could be designed for the treatment of tuberculosis by targeting MtSK.
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http://dx.doi.org/10.1021/acs.biochem.8b00231DOI Listing
August 2018

EpiProfile 2.0: A Computational Platform for Processing Epi-Proteomics Mass Spectrometry Data.

J Proteome Res 2018 07 30;17(7):2533-2541. Epub 2018 May 30.

Epigenetics Institute, Department of Biochemistry and Biophysics , Perelman School of Medicine University of Pennsylvania , Philadelphia , Pennsylvania 19104 , United States.

Epigenetics has become a fundamental scientific discipline with various implications for biology and medicine. Epigenetic marks, mostly DNA methylation and histone post-translational modifications (PTMs), play important roles in chromatin structure and function. Accurate quantification of these marks is an ongoing challenge due to the variety of modifications and their wide dynamic range of abundance. Here we present EpiProfile 2.0, an extended version of our 2015 software (v1.0), for accurate quantification of histone peptides based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. EpiProfile 2.0 is now optimized for data-independent acquisition through the use of precursor and fragment extracted ion chromatography to accurately determine the chromatographic profile and to discriminate isobaric forms of peptides. The software uses an intelligent retention time prediction trained on the analyzed samples to enable accurate peak detection. EpiProfile 2.0 supports label-free and isotopic labeling, different organisms, known sequence mutations in diseases, different derivatization strategies, and unusual PTMs (such as acyl-derived modifications). In summary, EpiProfile 2.0 is a universal and accurate platform for the quantification of histone marks via LC-MS/MS. Being the first software of its kind, we anticipate that EpiProfile 2.0 will play a fundamental role in epigenetic studies relevant to biology and translational medicine. EpiProfile is freely available at https://github.com/zfyuan/EpiProfile2.0_Family .
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http://dx.doi.org/10.1021/acs.jproteome.8b00133DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6387837PMC
July 2018

Mechanism of irreversible inhibition of Mycobacterium tuberculosis shikimate kinase by ilimaquinone.

Biochim Biophys Acta Proteins Proteom 2018 May - Jun;1866(5-6):731-739. Epub 2018 Apr 12.

Department of Drug Discovery and Development, Harrison School of Pharmacy, 3306 Walker Building, Auburn University, Auburn, AL 36849, USA. Electronic address:

Ilimaquinone (IQ), a marine sponge metabolite, has been considered as a potential therapeutic agent for various diseases due to its broad range of biological activities. We show that IQ irreversibly inactivates Mycobacterium tuberculosis shikimate kinase (MtSK) through covalent modification of the protein. Inactivation occurred with an apparent second-order rate constant of about 60 M s. Following reaction with IQ, LC-MS analyses of intact MtSK revealed covalent modification of MtSK by IQ, with the concomitant loss of a methoxy group, suggesting a Michael-addition mechanism. Evaluation of tryptic fragments of IQ-derivatized MtSK by MS/MS demonstrated that Ser and Thr residues were most frequently modified with lesser involvement of Lys and Tyr. In or near the MtSK active site, three residues of the P-loop (K15, S16, and T17) as well as S77, T111, and S44 showed evidence of IQ-dependent derivatization. Accordingly, inclusion of ATP in IQ reactions with MtSK partially protected the enzyme from inactivation and limited IQ-based derivatization of K15 and S16. Additionally, molecular docking models for MtSK-IQ were generated for IQ-derivatized S77 and T111. In the latter, ATP was observed to sterically clash with the IQ moiety. Out of three other enzymes evaluated, lactate dehydrogenase was derivatized and inactivated by IQ, but pyruvate kinase and catalase-peroxidase (KatG) were unaffected. Together, these data suggest that IQ is promiscuous (though not entirely indiscriminant) in its reactivity. As such, the potential of IQ as a lead in the development of antitubercular agents directed against MtSK or other targets is questionable.
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http://dx.doi.org/10.1016/j.bbapap.2018.04.007DOI Listing
July 2018

Integrating Proteomics and Targeted Metabolomics to Understand Global Changes in Histone Modifications.

Proteomics 2018 09 20;18(18):e1700309. Epub 2018 Apr 20.

Epigenetics Institute, Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.

The chromatin fiber is the control panel of eukaryotic cells. Chromatin is mostly composed of DNA, which contains the genetic instruction for cell phenotype, and histone proteins, which provide the scaffold for chromatin folding and part of the epigenetic inheritance. Histone writers/erasers "flag" chromatin regions by catalyzing/removing covalent histone post-translational modifications (PTMs). Histone PTMs chemically contribute to chromatin relaxation or compaction and recruit histone readers to modulate DNA readout. The precursors of protein PTMs are mostly small metabolites. For instance, acetyl-CoA is used for acetylation, ATP for phosphorylation, and S-adenosylmethionine for methylation. Interestingly, PTMs such as acetylation can occur at neutral pH also without their respective enzyme when the precursor is sufficiently concentrated. Therefore, it is essential to differentially quantify the contribution of histone writers/erasers versus the effect of local concentration of metabolites to understand the primary regulation of histone PTM abundance. Aberrant phenotypes such as cancer cells have misregulated metabolism and thus the composition and the modulation of chromatin is not only driven by enzymatic tuning. In this review, the latest advances in mass spectrometry (MS) to analyze histone PTMs and the most adopted quantification methods for related metabolites, both necessary to understand PTM relative changes, are discussed.
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http://dx.doi.org/10.1002/pmic.201700309DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6261489PMC
September 2018

Characterization of histone acylations links chromatin modifications with metabolism.

Nat Commun 2017 10 26;8(1):1141. Epub 2017 Oct 26.

Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA.

Over the last decade, numerous histone acyl post-translational modifications (acyl-PTMs) have been discovered, of which the functional significance is still under intense study. Here, we use high-resolution mass spectrometry to accurately quantify eight acyl-PTMs in vivo and after in vitro enzymatic assays. We assess the ability of seven histone acetyltransferases (HATs) to catalyze acylations on histones in vitro using short-chain acyl-CoA donors, proving that they are less efficient towards larger acyl-CoAs. We also observe that acyl-CoAs can acylate histones through non-enzymatic mechanisms. Using integrated metabolomic and proteomic approaches, we achieve high correlation (R  > 0.99) between the abundance of acyl-CoAs and their corresponding acyl-PTMs. Moreover, we observe a dose-dependent increase in histone acyl-PTM abundances in response to acyl-CoA supplementation in in nucleo reactions. This study represents a comprehensive profiling of scarcely investigated low-abundance histone marks, revealing that concentrations of acyl-CoAs affect histone acyl-PTM abundances by both enzymatic and non-enzymatic mechanisms.
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http://dx.doi.org/10.1038/s41467-017-01384-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5656686PMC
October 2017

Cytoplasmic chromatin triggers inflammation in senescence and cancer.

Nature 2017 10 4;550(7676):402-406. Epub 2017 Oct 4.

Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.

Chromatin is traditionally viewed as a nuclear entity that regulates gene expression and silencing. However, we recently discovered the presence of cytoplasmic chromatin fragments that pinch off from intact nuclei of primary cells during senescence, a form of terminal cell-cycle arrest associated with pro-inflammatory responses. The functional significance of chromatin in the cytoplasm is unclear. Here we show that cytoplasmic chromatin activates the innate immunity cytosolic DNA-sensing cGAS-STING (cyclic GMP-AMP synthase linked to stimulator of interferon genes) pathway, leading both to short-term inflammation to restrain activated oncogenes and to chronic inflammation that associates with tissue destruction and cancer. The cytoplasmic chromatin-cGAS-STING pathway promotes the senescence-associated secretory phenotype in primary human cells and in mice. Mice deficient in STING show impaired immuno-surveillance of oncogenic RAS and reduced tissue inflammation upon ionizing radiation. Furthermore, this pathway is activated in cancer cells, and correlates with pro-inflammatory gene expression in human cancers. Overall, our findings indicate that genomic DNA serves as a reservoir to initiate a pro-inflammatory pathway in the cytoplasm in senescence and cancer. Targeting the cytoplasmic chromatin-mediated pathway may hold promise in treating inflammation-related disorders.
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http://dx.doi.org/10.1038/nature24050DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5850938PMC
October 2017

Recognition of Histone H3K14 Acylation by MORF.

Structure 2017 04 9;25(4):650-654.e2. Epub 2017 Mar 9.

Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA. Electronic address:

The monocytic leukemia zinc-finger protein-related factor (MORF) is a transcriptional coactivator and a catalytic subunit of the lysine acetyltransferase complex implicated in cancer and developmental diseases. We have previously shown that the double plant homeodomain finger (DPF) of MORF is capable of binding to acetylated histone H3. Here we demonstrate that the DPF of MORF recognizes many newly identified acylation marks. The mass spectrometry study provides comprehensive analysis of H3K14 acylation states in vitro and in vivo. The crystal structure of the MORF DPF-H3K14butyryl complex offers insight into the selectivity of this reader toward lipophilic acyllysine substrates. Together, our findings support the mechanism by which the acetyltransferase MORF promotes spreading of histone acylation.
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http://dx.doi.org/10.1016/j.str.2017.02.003DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5415407PMC
April 2017

LC-MS-Based Quality Assessment of a Traditional Chinese Medicine YANG XIN Formulation.

Planta Med 2016 Aug 28;82(13):1208-16. Epub 2016 Apr 28.

Department of Drug Discovery and Development, Harrison School of Pharmacy, Auburn University, Auburn, Alabama, USA.

YANG XIN is a traditional Chinese medicine formulation used for nervous fatigue and consists of a proprietary blend of concentrated extracts from 18 plant ingredients. The 18 constituent plant ingredients, YANG XIN capsules, and formulations 2014-005_1 A and 1B were extracted by consecutive 24-hour macerations with dichloromethane followed by methanol. Metabolite separation was carried out through LC-MS in 40 minutes. Data acquisitions for qualitative and quantitative analyses of the samples were collected under (±) ESI modes and (+) APCI mode using full spectrum scan analysis.A total of 18 analytical markers were identified by LC-MS for YANG XIN formulations based on accurate mass measurements, molecular formula, double bond equivalent, MFG score, and error (ppm) of the measurement. Aditionally, a comparison of the data with previously reported results for the compounds, followed by identity confirmation with standard compounds, was performed. Seventeen analytical markers representing 17 plant ingredients in the different YANG XIN formulations were quantified for the first time. The YANG XIN capsules and the 2014-005_1B formulation were similar to each other and different from the 2014-005_1 A formulation based on the fact that both YANG XIN capsules and the 2014-005_1B formulation contain the same analytical markers. This method provides good linearity (r(2) > 0.9945), intraday precision (R. S. D. < 3.9 %), interday precision (R. S. D. < 5.6 %), accuracy (99.2-101 %), recovery (145.7 %), limit of detection (0.0011-0.0732 µg/mL), and limit of quantitation (0.0038-0.2441 µg/mL).
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http://dx.doi.org/10.1055/s-0042-106170DOI Listing
August 2016

Low Resolution Data-Independent Acquisition in an LTQ-Orbitrap Allows for Simplified and Fully Untargeted Analysis of Histone Modifications.

Anal Chem 2015 Nov 5;87(22):11448-54. Epub 2015 Nov 5.

Epigenetics Program, Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania , Room 9-124, 3400 Civic Center Boulevard, Building 421, Philadelphia, Pennsylvania 19104, United States.

Label-free peptide quantification in liquid chromatography-mass spectrometry (LC-MS) proteomics analyses is complicated by the presence of isobaric coeluting peptides, as they generate the same extracted ion chromatogram corresponding to the sum of their intensities. Histone proteins are especially prone to this, as they are heavily modified by post-translational modifications (PTMs). Their proteolytic digestion leads to a large number of peptides sharing the same mass, while carrying PTMs on different amino acid residues. We present an application of MS data-independent acquisition (DIA) to confidently determine and quantify modified histone peptides. By introducing the use of low-resolution MS/MS DIA, we demonstrate that the signals of 111 histone peptides could easily be extracted from LC-MS runs due to the relatively low sample complexity. By exploiting an LTQ-Orbitrap mass spectrometer, we parallelized MS and MS/MS scan events using the Orbitrap and the linear ion trap, respectively, decreasing the total scan time. This, in combination with large windows for MS/MS fragmentation (50 m/z) and multiple full scan events within a DIA duty cycle, led to a MS scan cycle speed of ∼45 full MS per minute, improving the definition of extracted LC-MS chromatogram profiles. By using such acquisition method, we achieved highly comparable results to our optimized acquisition method for histone peptide analysis (R(2) correlation > 0.98), which combines data-dependent acquisition (DDA) and targeted MS/MS scans, the latter targeting isobaric peptides. By using DIA, we could also remine our data set and quantify 16 additional isobaric peptides commonly not targeted during DDA experiments. Finally, we demonstrated that by performing the full MS scan in the linear ion trap, we achieve highly comparable results as when adopting high-resolution MS scans (R(2) correlation 0.97). Taken together, results confirmed that histone peptide analysis can be performed using DIA and low-resolution MS with high accuracy and precision of peptide quantification. Moreover, DIA intrinsically enables data remining to later identify and quantify isobaric peptides unknown at the time of the LC-MS experiment. These methods will open up epigenetics analyses to the proteomics community who do not have routine access to the newer generation high-resolution MS/MS generating instruments.
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http://dx.doi.org/10.1021/acs.analchem.5b03009DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4811372PMC
November 2015

Development of a functional assay to detect inhibitors of Plasmodium falciparum glutathione reductase utilizing liquid chromatography-mass spectrometry.

Biomed Chromatogr 2016 Apr 18;30(4):543-7. Epub 2015 Sep 18.

Department of Drug Discovery and Development, Harrison School of Pharmacy, 4306 Walker Building, Auburn University, Auburn, AL, 36849, USA.

Plasmodium falciparum (Pf) like most other organisms, has a sophisticated antioxidant system, part of which includes glutathione reductase (GR). GR works by recycling toxic glutathione disulfide to glutathione, thereby reducing reactive oxygen species and making a form of glutathione (GSH) the parasite can use. Inhibition of this enzyme in Pf impedes parasite growth. In addition, it has been confirmed that PfGR is not identical to human GR. Thus, PfGR is an excellent target for antimalarial drug development. A functional assay utilizing liquid chromatography-mass spectrometry was developed to specifically identify and evaluate inhibitors of PfGR. Using recombinant PfGR enzyme and 1,4-naphthoquinone (1) as a reference compound and 4-nitrobenzothiadiazole (2) and methylene blue (3) as additional compounds, we quantified the concentration of GSH produced compared with a control to determine the inhibitory effect of these compounds. Our results coincide with that presented in literature: compounds 1-3 inhibit PfGR with IC50 values of 2.71, 8.38, and 19.23 µm, respectively. Good precision for this assay was exhibited by low values of intraday and interday coefficient of variation (3.1 and 2.4%, respectively). Thus, this assay can be used to screen for other potential inhibitors of PfGR quickly and accurately.
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http://dx.doi.org/10.1002/bmc.3580DOI Listing
April 2016

Selective Mycobacterium tuberculosis Shikimate Kinase Inhibitors as Potential Antibacterials.

Perspect Medicin Chem 2015 15;7:9-20. Epub 2015 Mar 15.

Department of Drug Discovery and Development, Harrison School of Pharmacy, Auburn University, Auburn, AL, USA.

Owing to the persistence of tuberculosis (TB) as well as the emergence of multidrug-resistant and extensively drug-resistant (XDR) forms of the disease, the development of new antitubercular drugs is crucial. Developing inhibitors of shikimate kinase (SK) in the shikimate pathway will provide a selective target for antitubercular agents. Many studies have used in silico technology to identify compounds that are anticipated to interact with and inhibit SK. To a much more limited extent, SK inhibition has been evaluated by in vitro methods with purified enzyme. Currently, there are no data on in vivo activity of Mycobacterium tuberculosis shikimate kinase (MtSK) inhibitors available in the literature. In this review, we present a summary of the progress of SK inhibitor discovery and evaluation with particular attention toward development of new antitubercular agents.
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http://dx.doi.org/10.4137/PMC.S13212DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4362912PMC
April 2015

Development of an ESI-LC-MS-based assay for kinetic evaluation of Mycobacterium tuberculosis shikimate kinase activity and inhibition.

Anal Chem 2015 Feb 28;87(4):2129-36. Epub 2015 Jan 28.

Department of Drug Discovery and Development, Harrison School of Pharmacy, Auburn University , 4306 Walker Building, Auburn, Alabama 36849, United States.

A simple and reliable liquid chromatography-mass spectrometry (LC-MS) assay has been developed and validated for the kinetic characterization and evaluation of inhibitors of shikimate kinase from Mycobacterium tuberculosis (MtSK), a potential target for the development of novel antitubercular drugs. This assay is based on the direct determination of the reaction product shikimate-3-phosphate (S3P) using electrospray ionization (ESI) and a quadrupole time-of-flight (Q-TOF) detector. A comparative analysis of the kinetic parameters of MtSK obtained by the LC-MS assay with those obtained by a conventional UV-assay was performed. Kinetic parameters determined by LC-MS were in excellent agreement with those obtained from the UV assay, demonstrating the accuracy, and reliability of this method. The validated assay was successfully applied to the kinetic characterization of a known inhibitor of shikimate kinase; inhibition constants and mode of inhibition were accurately delineated with LC-MS.
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http://dx.doi.org/10.1021/ac503210nDOI Listing
February 2015

Identification of shikimate kinase inhibitors among anti-Mycobacterium tuberculosis compounds by LC-MS.

Tuberculosis (Edinb) 2014 Mar 31;94(2):152-8. Epub 2013 Dec 31.

Department of Pharmacal Sciences, Harrison School of Pharmacy, 4306 Walker Building, Auburn University, Auburn, AL 36849, USA. Electronic address:

Increasing drug resistance has challenged the control and treatment of tuberculosis, sparking recent interest in finding new antitubercular agents with different chemical scaffolds and mechanisms of action. Mycobacterium tuberculosis shikimate kinase (MtSK), an enzyme present in the shikimate pathway in bacteria, is essential for the survival of the tubercle bacillus, representing an ideal target for therapeutic intervention given its absence in mammals. In this study, a small library of 404 synthetic antimycobacterial compounds identified and supplied through the NIH Tuberculosis Antimicrobial Acquisition and Coordinating Facility (TAACF) high throughput screening program against whole cell M. tuberculosis H37Rv was further screened using a mass spectrometry-based functional assay in order to identify a potential enzymatic target. Fourteen compounds containing an oxadiazole-amide or a 2-aminobenzothiazole core scaffold showed MtSK inhibitory activity at 50 μM, with the lowest giving an IC50 of 1.94 μM. Induced fit docking studies suggested that the scaffolds shared by these compounds fit well in the shikimate binding pocket of MtSK. In summary, we report new early discovery stage lead scaffolds targeting the essential protein MtSK that can be further pursued in a rational drug design program for the discovery of more selective antitubercular drugs.
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http://dx.doi.org/10.1016/j.tube.2013.12.004DOI Listing
March 2014

Triterpenes from Warszewiczia coccinea (Rubiaceae) as inhibitors of acetylcholinesterase.

Nat Prod Commun 2009 Oct;4(10):1323-6

Department of Pharmacal Sciences, Harrison School of Pharmacy, Auburn University, 4306B Walker Building, Auburn, AL 36849, USA.

Seventy-six plant extracts from the Panamanian flora have been screened for acetylcholinesterase (AChE) inhibitors by thin-layer chromatography (TLC) bioautography. The most promising extracts with AChE inhibitory and free radical scavenging activities at 100 microg were those of Tabernaemontana panamensis (Markgr., Boiteau & L. Allorge) Leeuwenb., Pentagonia macrophylla Benth., and Warszewiczia coccinea (Vahl) Klotzsch. Bioguided fractionation of W. coccinea stem extract afforded two triterpenes, 3beta,6beta,19alpha-trihydroxy-urs-12-en-28-oic acid (1) and 3beta,6beta-dihydroxy-olean-12-en-28-oic acid (sumaresinolic acid) (2), with AChE inhibitory activity. Their structures were determined by spectroscopic methods. This is the first report of these bioactive triterpenes in W. coccinea.
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October 2009
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