Identification of novel diphenyl urea inhibitors of Mt-GuaB2 active against Mycobacterium tuberculosis

School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
Microbiology (Impact Factor: 2.56). 11/2010; 157(Pt 1):290-9. DOI: 10.1099/mic.0.042549-0
Source: PubMed


In contrast with most bacteria, which harbour a single inosine monophosphate dehydrogenase (IMPDH) gene, the genomic sequence of Mycobacterium tuberculosis H37Rv predicts three genes encoding IMPDH: guaB1, guaB2 and guaB3. These three genes were cloned and expressed in Escherichia coli to evaluate functional IMPDH activity. Purified recombinant Mt-GuaB2, which uses inosine monophosphate as a substrate, was identified as the only active GuaB orthologue in M. tuberculosis and showed optimal activity at pH 8.5 and 37 °C. Mt-GuaB2 was inhibited significantly in vitro by a panel of diphenyl urea-based derivatives, which were also potent anti-mycobacterial agents against M. tuberculosis and Mycobacterium smegmatis, with MICs in the range of 0.2-0.5 μg ml(-1). When Mt-GuaB2 was overexpressed on a plasmid in trans in M. smegmatis, a diphenyl urea analogue showed a 16-fold increase in MIC. Interestingly, when Mt-GuaB orthologues (Mt-GuaB1 and 3) were also overexpressed on a plasmid in trans in M. smegmatis, they also conferred resistance, suggesting that although these Mt-GuaB orthologues were inactive in vitro, they presumably titrate the effect of the inhibitory properties of the active compounds in vivo.

Full-text preview

Available from:
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Effect of waste water execrated from milk dairy on to the soil physicochemical, biological and enzymatic activities like protease, phosphotase was studied in the present study. Discharge of dairy milk effluents alters the physicochemical, biological and enzymatic activities. These changes included increased in pH, water holding capacity, electrical conductivity, Carbon, Nitrogen and Phosphorus in contaminated soil. Higher bacterial and lower fungal populations recorded in the polluted soil. Increased protease, phosphotase activities were observed in soil discharged with dairy waste water from the industry.
    Full-text · Article · Jan 2009 · Asian Journal of Microbiology, Biotechnology and Environmental Sciences
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The treatment of tuberculosis is becoming more difficult due to the ever increasing prevalence of drug resistance. Thus, it is imperative that novel anti-tuberculosis agents, with unique mechanisms of action, be discovered and developed. The direct anti-tubercular testing of a small compound library led to discovery of adamantyl urea hit compound 1. In this study, the hit was followed up through the synthesis of an optimization library. This library was generated by systematically replacing each section of the molecule with a similar moiety until a clear structure-activity relationship was obtained with respect to anti-tubercular activity. The best compounds in this series contained a 1-adamantyl-3-phenyl urea core and had potent activity against Mycobacterium tuberculosis plus an acceptable therapeutic index. It was noted that the compounds identified and the pharmacophore developed is consistent with inhibitors of epoxide hydrolase family of enzymes. Consequently, the compounds were tested for inhibition of representative epoxide hydrolases: M. tuberculosis EphB and EphE; and human soluble epoxide hydrolase. Many of the optimized inhibitors showed both potent EphB and EphE inhibition suggesting the antitubercular activity is through inhibition of multiple epoxide hydrolase enzymes. The inhibitors also showed potent inhibition of humans soluble epoxide hydrolase, but limited cytotoxicity suggesting that future studies must be towards increasing the selectivity of epoxide hydrolase inhibition towards the M. tuberculosis enzymes.
    Full-text · Article · Jul 2011 · Bioorganic & medicinal chemistry
  • [Show abstract] [Hide abstract]
    ABSTRACT: Introduction: Target driven drug discovery is a long and arduous task requiring a huge investment of time, energy and resources. Therefore, it is very important to select targets which provide the maximum chance of obtaining inhibitors that will be efficacious in animal models and finally in tuberculosis (TB) patients. Areas covered: The article discusses the necessity for new targets in Mycobacterium tuberculosis (Mtb) drug discovery and how the functional redundancy of putative targets in Mtb adds a new dimension to the complexity of validation. The article also reviews survival kinetics using conditional knockout (KO) or knockdown (KD) strains and discusses how this has provided crucial information on target vulnerability. Furthermore, the article also comments on how the chemical validation of new targets using specific inhibitors has greatly supplemented the genetic validation efforts. Expert opinion: Because of complexity of pathogenesis of TB, the putative drug targets need to be validated under multiple physiological conditions. Target protein depletion can mimic chemical inhibition and, therefore, will be a valuable tool in predicting the vulnerability of a target. Conditional KO or KD makes it possible to study the phenotypes of Mtb strains under a variety of physiological states. The phenotype of these strains should also be tested in animal models which mimic human TB more closely. Finally, inhibitors with confirmed mode of action can be important tools for validating Mtb drug targets.
    No preview · Article · Nov 2011 · Expert Opinion on Drug Discovery
Show more