Inhibition of a Mycobacterium tuberculosis β-Ketoacyl ACP Synthase by Isoniazid

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Science  05 Jun 1998:
Vol. 280, Issue 5369, pp. 1607-1610
DOI: 10.1126/science.280.5369.1607

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Although isoniazid (isonicotinic acid hydrazide, INH) is widely used for the treatment of tuberculosis, its molecular target has remained elusive. In response to INH treatment, saturated hexacosanoic acid (C26:0) accumulated on a 12-kilodalton acyl carrier protein (AcpM) that normally carried mycolic acid precursors as long as C50. A protein species purified from INH-treated Mycobacterium tuberculosis was shown to consist of a covalent complex of INH, AcpM, and a β-ketoacyl acyl carrier protein synthase, KasA. Amino acid–altering mutations in the KasA protein were identified in INH-resistant patient isolates that lacked other mutations associated with resistance to this drug.

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