The tuberculosis prodrug isoniazid bound to activating peroxidases
The tuberculosis prodrug isoniazid bound to activating peroxidases
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DOI：
10.1074/jbc.m707412200
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发表时间：
2008-03-07
影响因子：
4.8
通讯作者：
Moody, Peter C. E.
中科院分区：
文献类型：
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作者：
Metcalfe, Clive;Macdonald, Isabel K.;Moody, Peter C. E.
异烟肼（INH，异烟酸肼）是仅有的两种有效治疗结核病的药物之一。这种前药被结核分枝杆菌内源性的血红素酶过氧化氢酶过氧化物酶（KatG）激活，但激活机制尚不清楚，部分原因是其结合相互作用尚未正确确定。第一类过氧化物酶抗坏血酸过氧化物酶（APX）和细胞色素c过氧化物酶（CcP）具有与KatG非常相似的活性位点结构，也能够激活异烟肼。本文报道了异烟肼与APX和CcP结合的第一个晶体结构。这是异烟肼与任何激活酶结合的第一个结构。结构表明，异烟肼结合在APX和CcP的δ血红素边缘附近，尽管两种情况下的精确结合方向略有不同。在APX中，在靠近抗坏血酸结合位点的γ -血红素边缘发现了INH的第二个结合位点，这表明γ -血红素边缘也可以支持芳香底物的结合。我们还发现，在大豆APX的一个活性位点突变体（W41A）中，当远端组氨酸被丙氨酸（H42A）取代时，INH可以直接结合到血红素铁上成为抑制剂，并以不同的模式结合。这些结构为I类过氧化物酶中异烟肼结合位点的定位提供了第一个明确的证据，并为自然发生的结核分枝杆菌KatG突变株的异烟肼耐药性提供了合理的解释。
Isoniazid (INH, isonicotinic acid hydrazine) is one of only two therapeutic agents effective in treating tuberculosis. This prodrug is activated by the heme enzyme catalase peroxidase (KatG) endogenous to Mycobacterium tuberculosis but the mechanism of activation is poorly understood, in part because the binding interaction has not been properly established. The class I peroxidases ascorbate peroxidase (APX) and cytochrome c peroxidase (CcP) have active site structures very similar to KatG and are also capable of activating isoniazid. We report here the first crystal structures of complexes of isoniazid bound to APX and CcP. These are the first structures of isoniazid bound to any activating enzymes. The structures show that isoniazid binds close to the delta-heme edge in both APX and CcP, although the precise binding orientation varies slightly in the two cases. A second binding site for INH is found in APX at the gamma-heme edge close to the established ascorbate binding site, indicating that the gamma-heme edge can also support the binding of aromatic substrates. We also show that in an active site mutant of soybean APX (W41A) INH can bind directly to the heme iron to become an inhibitor and in a different mode when the distal histidine is replaced by alanine (H42A). These structures provide the first unambiguous evidence for the location of the isoniazid binding site in the class I peroxidases and provide rationalization of isoniazid resistance in naturally occurring KatG mutant strains of M. tuberculosis.