Isoniazid affects multiple components of the type II fatty acid synthase system of Mycobacterium tuberculosis
Isoniazid affects multiple components of the type II fatty acid synthase system of Mycobacterium tuberculosis
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DOI：
10.1046/j.1365-2958.2000.02145.x
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发表时间：
2000-11-01
影响因子：
3.6
通讯作者：
Barry, CE
中科院分区：
文献类型：
--
作者：
Slayden, RA;Lee, RE;Barry, CE
遗传和生化证据表明，异烟肼（INH）的两种不同的靶酶在独特的II型脂肪酸合酶（FAS）系统中参与分枝菌酸的生产。这两种组分是烯酰酰基载体蛋白（ACP）还原酶InhA和β-酮脂酰-ACP合酶KasA。我们比较了INH治疗结核分枝杆菌（MTB）与两种具有明确靶点的抑制剂的结果：三氯生（TRC），抑制InhA;硫代乳霉素（TLM），抑制KasA。INH和TLM（但不是TRC）上调含有五种FAS II组分（包括kasA和acpM）的操纵子的表达。虽然所有三种化合物都抑制分枝菌酸合成，但用INH和TLM处理，而不是用TRC处理，导致ACP结合的脂质前体积累为26个碳长且完全饱和的分枝菌酸。结核分枝杆菌耐TLM突变株对INH的交叉耐药率高于耐TRC突变株。过表达KasA的小鼠对TLM和INH的耐药性高于TRC。过表达InhA的小鼠对TRC的耐药性高于INH和TLM。InhA和KasA的共过表达导致INH抗性水平的强烈增强，以及对TLM和TRC的交叉抗性。这些结果表明，FAS II复合物的这些组分不是独立调节的，InhA表达水平的改变影响KasA的表达水平。尽管如此，INH似乎在总体作用模式上更接近TLM，并且KasA水平似乎与INH敏感性密切相关。
Genetic and biochemical evidence has implicated two different target enzymes for isoniazid (INH) within the unique type II fatty acid synthase (FAS) system involved in the production of mycolic acids. These two components are an enoyl acyl carrier protein (ACP) reductase, InhA, and a beta -ketoacyl-ACP synthase, KasA. We compared the consequences of INH treatment of Mycobacterium tuberculosis (MTB) with two inhibitors having well-defined targets: triclosan (TRC), which inhibits InhA; and thiolactomycin (TLM), which inhibits KasA. INH and TLM, but not TRC, upregulate the expression of an operon containing five FAS II components, including kasA and acpM. Although all three compounds inhibit mycolic acid synthesis, treatment with INH and TLM, but not with TRC, results in the accumulation of ACP-bound lipid precursors to mycolic acids that were 26 carbons long and fully saturated. TLM-resistant mutants of MTB were more cross-resistant to INH than TRC-resistant mutants. Overexpression of KasA conferred more resistance to TLM and INH than to TRC. Overexpression of InhA conferred more resistance to TRC than to INH and TLM. Co-overexpression of both InhA and KasA resulted in strongly enhanced levels of INH resistance, in addition to cross-resistance to both TLM and TRC. These results suggest that these components of the FAS II complex are not independently regulated and that alterations in the expression level of InhA affect expression levels of KasA. Nonetheless, INH appeared to resemble TLM more closely in overall mode of action, and KasA levels appeared to be tightly correlated with INH sensitivity.