title: Synthesis and biological evaluation of NAS-21 and NAS-91 analogues as potential inhibitors of the mycobacterial FAS-II dehydratase enzyme Rv0636.
abstract: The identification of potential new anti-tubercular chemotherapeutics is paramount due to the recent emergence of extensively drug-resistant strains of Mycobacterium tuberculosis (XDR-TB). Libraries of NAS-21 and NAS-91 analogues were synthesized and evaluated for their whole-cell activity against Mycobacterium bovis BCG. NAS-21 analogues 1 and 2 demonstrated enhanced whole-cell activity in comparison to the parental compound, and an M. bovis BCG strain overexpressing the dehydratase enzyme Rv0636 was resistant to these analogues. NAS-91 analogues with ortho-modifications gave enhanced whole-cell activity. However, extension with biphenyl modifications compromised the whole-cell activities of both NAS-21 and NAS-91 analogues. Interestingly, both libraries demonstrated in vitro activity against fatty acid synthase II (FAS-II) but not FAS-I in cell-free extracts. In in vitro assays of FAS-II inhibition, NAS-21 analogues 4 and 5 had IC(50) values of 28 and 19 mug ml(-1), respectively, for the control M. bovis strain, and the M. bovis BCG strain overexpressing Rv0636 showed a marked increase in resistance. In contrast, NAS-91 analogues demonstrated moderate in vitro activity, although increased resistance was again observed in FAS-II activity assays with the Rv0636-overexpressing strain. Fatty acid methyl ester (FAME) and mycolic acid methyl ester (MAME) analysis of M. bovis BCG and the Rv0636-overexpressing strain revealed that the effect of the drug was relieved in the overexpressing strain, further implicating and potentially identifying Rv0636 as the target for these known FabZ dehydratase inhibitors. This study has identified candidates for further development as drug therapeutics against the mycobacterial FAS-II dehydratase enzyme.
authors.affiliation: University of Birmingham, School of Biosciences, Edgbaston, Birmingham B15 2TT, UK.
authors.forename: Veemal
authors.initials: V
authors.lastname: Bhowruth
authors.affiliation: University of Birmingham, School of Biosciences, Edgbaston, Birmingham B15 2TT, UK.
authors.forename: Alistair K
authors.initials: AK
authors.lastname: Brown
authors.affiliation: University of Birmingham, School of Biosciences, Edgbaston, Birmingham B15 2TT, UK.
authors.forename: Gurdyal S
authors.initials: GS
authors.lastname: Besra
mesh_terms: D000995:Antitubercular Agents / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D054889:Fatty Acid Synthase, Type II / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D064429:Fatty Acid Synthases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D005419:Flavonoids / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D006801:Humans; D009161:Mycobacterium / Q000187:drug effects* / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D009164:Mycobacterium Infections / Q000188:drug therapy* / Q000382:microbiology; D054852:Small Molecule Libraries / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology
chemical_list: D000995:Antitubercular Agents; D001426:Bacterial Proteins; D004791:Enzyme Inhibitors; D005419:Flavonoids; D054852:Small Molecule Libraries; D064429:Fatty Acid Synthases; D054889:Fatty Acid Synthase, Type II; C413881:fatty acid synthase I, mycobacteria