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Antimicrobial Agents and Chemotherapy, 12 1996, 2813-2819, Vol 40, No. 12
RA Slayden, RE Lee, JW Armour, AM Cooper, IM Orme, PJ Brennan and GS Besra
Thiolactomycin (TLM) possesses in vivo antimycobacterial activity against
the saprophytic strain Mycobacterium smegmatis mc2155 and the virulent
strain M. tuberculosis Erdman, resulting in complete inhibition of growth
on solid media at 75 and 25 micrograms/ml, respectively. Use of an in vitro
murine macrophage model also demonstrated the killing of viable
intracellular M. tuberculosis in a dose-dependent manner. Through the use
of in vivo [1,2-14C]acetate labeling of M. smegmatis, TLM was shown to
inhibit the synthesis of both fatty acids and mycolic acids. However,
synthesis of the shorter- chain alpha'-mycolates of M. smegmatis was not
inhibited by TLM, whereas synthesis of the characteristic longer-chain
alpha-mycolates and epoxymycolates was almost completely inhibited at 75
micrograms/ml. The use of M. smegmatis cell extracts demonstrated that TLM
specifically inhibited the mycobacterial acyl carrier protein-dependent
type II fatty acid synthase (FAS-II) but not the multifunctional type I
fatty acid synthase (FAS-I). In addition, selective inhibition of long-
chain mycolate synthesis by TLM was demonstrated in a dose-response manner
in purified, cell wall-containing extracts of M. smegmatis cells. The in
vivo and in vitro data and knowledge of the mechanism of TLM resistance in
Escherichia coli suggest that two distinct TLM targets exist in
mycobacteria, the beta-ketoacyl-acyl carrier protein synthases involved in
FAS-II and the elongation steps leading to the synthesis of the
alpha-mycolates and oxygenated mycolates. The efficacy of TLM against M.
smegmatis and M. tuberculosis provides the prospects of identifying fatty
acid and mycolic acid biosynthetic genes and revealing a novel range of
chemotherapeutic agents directed against M. tuberculosis.
Copyright © 1996 by the American Society for Microbiology. All rights reserved.
Antimycobacterial action of thiolactomycin: an inhibitor of fatty acid and mycolic acid synthesis
Department of Microbiology, Colorado State University, Fort Collins 80523-1677, USA.
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