Unique Mechanism of Action of the Thiourea Drug Isoxyl on Mycobacterium tuberculosis

Benjawan Phetsuksiri, Mary Jackson, Hataichanok Scherman, Michael McNeil, Gurdyal S. Besra, Alain R. Baulard, Richard A. Slayden, Andrea De Barber, Clifton E. Barry, Mark S. Baird, Dean C. Crick, Patrick J. Brennan

Research output: Contribution to journalArticle

113 Citations (Scopus)

Abstract

The thiourea isoxyl (thiocarlide; 4,4′-diisoamyloxydiphenylthiourea) is known to be an effective anti-tuberculosis drug, active against a range of multidrug-resistant strains of Mycobacterium tuberculosis and has been used clinically. Little was known of its mode of action. We now demonstrate that isoxyl results in a dose-dependent decrease in the synthesis of oleic and, consequently, tuberculostearic acid in M. tuberculosis with complete inhibition at 3 μg/ml. Synthesis of mycolic acid was also affected. The anti-bacterial effect of isoxyl was partially reversed by supplementing growth medium with oleic acid. The specificity of this inhibition pointed to a Δ9-stearoyl desaturase as the drug target. Development of a cell-free assay for Δ9-desaturase activity allowed direct demonstration of the inhibition of oleic acid synthesis by isoxyl. Interestingly, sterculic acid, a known inhibitor of Δ9-desaturases, emulated the effect of isoxyl on oleic acid synthesis but did not affect mycolic acid synthesis, demonstrating the lack of a relationship between the two effects of the drug. The three putative fatty acid desaturases in the M. tuberculosis genome, desA1, desA2, and desA3, were cloned and expressed in Mycobacterium bovis BCG. Cell-free assays and whole cell labeling demonstrated increased Δ9-desaturase activity and oleic acid synthesis only in the desA3-overexpressing strain and an increase in the minimal inhibitory concentration for isoxyl, indicating that DesA3 is the target of the drug. These results validate membrane-bound Δ9-desaturase, DesA3, as a new therapeutic target, and the thioureas as anti-tuberculosis drugs worthy of further development.

Original languageEnglish (US)
Pages (from-to)53123-53130
Number of pages8
JournalJournal of Biological Chemistry
Volume278
Issue number52
DOIs
StatePublished - Dec 26 2003
Externally publishedYes

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Thiourea
Mycobacterium tuberculosis
Oleic Acid
Pharmaceutical Preparations
Mycolic Acids
Mycobacterium bovis
Assays
Tuberculosis
Fatty Acid Desaturases
thiocarlide
Labeling
Demonstrations
Genes
Genome
Membranes
Growth

ASJC Scopus subject areas

  • Biochemistry

Cite this

Phetsuksiri, B., Jackson, M., Scherman, H., McNeil, M., Besra, G. S., Baulard, A. R., ... Brennan, P. J. (2003). Unique Mechanism of Action of the Thiourea Drug Isoxyl on Mycobacterium tuberculosis. Journal of Biological Chemistry, 278(52), 53123-53130. https://doi.org/10.1074/jbc.M311209200

Unique Mechanism of Action of the Thiourea Drug Isoxyl on Mycobacterium tuberculosis. / Phetsuksiri, Benjawan; Jackson, Mary; Scherman, Hataichanok; McNeil, Michael; Besra, Gurdyal S.; Baulard, Alain R.; Slayden, Richard A.; De Barber, Andrea; Barry, Clifton E.; Baird, Mark S.; Crick, Dean C.; Brennan, Patrick J.

In: Journal of Biological Chemistry, Vol. 278, No. 52, 26.12.2003, p. 53123-53130.

Research output: Contribution to journalArticle

Phetsuksiri, B, Jackson, M, Scherman, H, McNeil, M, Besra, GS, Baulard, AR, Slayden, RA, De Barber, A, Barry, CE, Baird, MS, Crick, DC & Brennan, PJ 2003, 'Unique Mechanism of Action of the Thiourea Drug Isoxyl on Mycobacterium tuberculosis', Journal of Biological Chemistry, vol. 278, no. 52, pp. 53123-53130. https://doi.org/10.1074/jbc.M311209200
Phetsuksiri B, Jackson M, Scherman H, McNeil M, Besra GS, Baulard AR et al. Unique Mechanism of Action of the Thiourea Drug Isoxyl on Mycobacterium tuberculosis. Journal of Biological Chemistry. 2003 Dec 26;278(52):53123-53130. https://doi.org/10.1074/jbc.M311209200
Phetsuksiri, Benjawan ; Jackson, Mary ; Scherman, Hataichanok ; McNeil, Michael ; Besra, Gurdyal S. ; Baulard, Alain R. ; Slayden, Richard A. ; De Barber, Andrea ; Barry, Clifton E. ; Baird, Mark S. ; Crick, Dean C. ; Brennan, Patrick J. / Unique Mechanism of Action of the Thiourea Drug Isoxyl on Mycobacterium tuberculosis. In: Journal of Biological Chemistry. 2003 ; Vol. 278, No. 52. pp. 53123-53130.
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