Inhibition of the bacterial enoyl reductase FabI by triclosan: a structure-reactivity analysis of FabI inhibition by triclosan analogues.
Inhibition of the bacterial enoyl reductase FabI by triclosan: a structure-reactivity analysis of FabI inhibition by triclosan analogues.
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DOI：
10.1021/jm030182i
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发表时间：
2004-01
影响因子：
7.3
通讯作者：
Sharada Sivaraman;Todd J. Sullivan;F. Johnson;P. Novichenok;Guanglei Cui;Carlos Simmerling;P. Tonge
中科院分区：
文献类型：
--
作者：
Sharada Sivaraman;Todd J. Sullivan;F. Johnson;P. Novichenok;Guanglei Cui;Carlos Simmerling;P. Tonge
为了探索三氯生对FabI（大肠杆菌II型脂肪酸生物合成途径中的烯酰还原酶）的皮摩尔亲和力的分子基础，使用一系列三氯生类似物进行了SAR研究。三氯生（1）是FabI的一种缓慢、紧密结合的抑制剂，与E.NAD（+）形式的酶特异性相互作用，K（1）值为7 pM。相比之下，2-苯氧基苯酚（2）与E.NAD（+）（K（1）= 0.5 μ M）和E.NADH（K（2）= 0.4 μ M）形式的酶具有相同的亲和力，并且缺乏三氯生观察到的缓慢结合步骤。因此，去除三个三氯生氯原子会使抑制剂对FabI的亲和力降低70，000倍，并消除对E.NAD（+）FabI复合物的偏好。5-氯-2-苯氧基苯酚（3）是FabI的一种缓慢、紧密结合的抑制剂，与酶的E.NAD（+）形式（K（1）= 1.1 pM）的结合强度是三氯生的7倍。因此，虽然FabI抑制不需要两个环B氯原子，但取代环A氯使结合亲和力增加450，000倍。鉴于这一显著的观察结果，SAR研究扩展到5-氟-2-苯氧基苯酚（4）和5-甲基-2-苯氧基苯酚（5）类似物，以进一步探索环A取代基的作用。虽然4和5都是缓慢、紧密结合的抑制剂，但它们与FabI的结合强度远低于三氯生。化合物4结合酶的E.NAD（+）和E.NADH形式，K（1）和K（2）值分别为3.2和240 nM，而化合物5仅结合E.NADH酶复合物，K（2）值为7.2 nM。因此，环A取代基是绝对需要的缓慢，紧密结合的抑制。此外，结合简单静电计算的pK（a）测量表明，环A取代基与F203的相互作用是控制类似物3-5对含有氧化形式辅因子的FabI复合物的亲和力的主要因素。
To explore the molecular basis for the picomolar affinity of triclosan for FabI, the enoyl reductase enzyme from the type II fatty acid biosynthesis pathway in Escherichia coli, an SAR study has been conducted using a series of triclosan analogues. Triclosan (1) is a slow, tight-binding inhibitor of FabI, interacting specifically with the E.NAD(+) form of the enzyme with a K(1) value of 7 pM. In contrast, 2-phenoxyphenol (2) binds with equal affinity to the E.NAD(+) (K(1) = 0.5 microM) and E.NADH (K(2) = 0.4 microM) forms of the enzyme and lacks the slow-binding step observed for triclosan. Thus, removal of the three triclosan chlorine atoms reduces the affinity of the inhibitor for FabI by 70,000-fold and removes the preference for the E.NAD(+) FabI complex. 5-Chloro-2-phenoxyphenol (3) is a slow, tight-binding inhibitor of FabI and binds to the E.NAD(+) form of the enzyme (K(1) = 1.1 pM) 7-fold more tightly than triclosan. Thus, while the two ring B chlorine atoms are not required for FabI inhibition, replacement of the ring A chlorine increases binding affinity by 450,000-fold. Given this remarkable observation, the SAR study was extended to the 5-fluoro-2-phenoxyphenol (4) and 5-methyl-2-phenoxyphenol (5) analogues to further explore the role of the ring A substituent. While both 4 and 5 are slow, tight-binding inhibitors, they bind substantially less tightly to FabI than triclosan. Compound 4 binds to both E.NAD(+) and E.NADH forms of the enzyme with K(1) and K(2) values of 3.2 and 240 nM, respectively, whereas compound 5 binds exclusively to the E.NADH enzyme complex with a K(2) value of 7.2 nM. Thus, the ring A substituent is absolutely required for slow, tight-binding inhibition. In addition, pK(a) measurements coupled with simple electrostatic calculations suggest that the interaction of the ring A substituent with F203 is a major factor in governing the affinity of analogues 3-5 for the FabI complex containing the oxidized form of the cofactor.