Identification of Glu166 as the general base in the acylation reaction of class A β-lactamases through QM/MM modeling
Identification of Glu166 as the general base in the acylation reaction of class A β-lactamases through QM/MM modeling
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DOI：
10.1021/ja034434g
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发表时间：
2003-08-13
影响因子：
15
通讯作者：
Höltje, HD
中科院分区：
文献类型：
--
作者：
Hermann, JC;Ridder, L;Höltje, HD
细菌A类β-内酰胺酶是最已知的对β-内酰胺抗生素的耐药性的原因。随着抗生素耐药性的持续上升，在开发有效的治疗剂和策略中需要改进对这些酶的作用机制的了解。A类β-内酰胺酶中的脱酰步骤的机制是公认的。相反，酰化步骤的机制一直不确定，提出了几个相互矛盾的建议。我们用量子力学/分子力学相结合的方法模拟了A类β-内酰胺酶的酰化反应。结果提供了一个原子水平的反应描述，并表明，Glu 166作为反应中的一般碱，通过居间的水分子去质子化Ser 70。Ser 70在协同反应中作为亲核试剂攻击内酰胺环。结果并不排除Lys 73在催化中的重要性，与实验数据一致。
Bacterial class A β-lactamases are responsible for the most known resistance against β-lactam antibiotics. With the continuing rise in antibiotic resistance, improved knowledge of the mechanisms of action of these enzymes is needed in the development of effective therapeutic agents and strategies. The mechanism of the deacylation step in class A β-lactamases is well accepted. In contrast, the mechanism of the acylation step has been uncertain, with several conflicting proposals put forward. We have modeled the acylation step in a class A β-lactamase, using a combined quantum mechanics/molecular mechanics approach. The results provide an atomic level description of the reaction and show that Glu166 acts as the general base in the reaction, deprotonating Ser70 via an intervening water molecule. Ser70 acts as the nucleophile for attack on the lactam ring in a concerted reaction. The results do not rule out the importance of Lys73 in catalysis, in agreement with experimental data.