2012年11月14日 讯 /生物谷BIOON/ --近日，刊登在国际杂志Journal of the American Chemical Society (JACS)上的一篇研究报告中，来自布里斯托大学和葡萄牙阿威罗大学的研究者通过研究揭示了一种特定酶的结构，这种酶可以破坏碳青霉烯类抗生素，抑制抗生素发挥作用，这种抗生素可以抑制一系列的严重感染。
细菌如大肠杆菌可以通过产生特定的碳青霉烯酶来抑制碳青霉烯类抗生素作用的发挥，从而来破坏其抗菌活性，继续进行感染。碳青霉烯酶是细菌β内酰胺酶的家族成员，β内酰胺酶可以破坏青霉素类及其相关的抗生素，但是为何碳青霉烯酶可以破坏碳青霉烯类抗生素（其它β内酰胺酶不能破坏）的分子机制并不清楚。
在这项研究中，研究者使用分子动力学模型，揭示了特定类型的碳青霉烯酶如何结合至抗生素，并促进其破坏使其效用失效。研究者使用X射线晶体衍射技术对碳青霉烯酶破坏碳青霉烯类抗生素的过程进行拍照，随后进行动态模拟实验模拟抗生素被破坏的过程。
在模拟过程中，研究者就可以看到碳青霉烯类抗生素被破坏的详细过程，理解此过程可以帮助研究者开发出新型的药物来抑制碳青霉烯类抗生素被破坏。
研究者Spencer说，结合实验技术和计算机技术我们就可以得到细菌对抗生素产生耐药的一系列起源信息，我们的晶体学结果揭示了抗生素被破坏的全部过程，这就为开发新型细菌酶类结合药物，来抑制细菌耐药性提供了基础。
研究者最后表示，识别细菌酶类和抗生素的分子反应，对于我们开发新型修饰药物来克服细菌的抗生素耐药性带来了很大帮助。（生物谷Bioon.com）
编译自：Understanding Antibiotic Resistance Using Crystallography and Computation
doi:10.1021/ja304460j
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The Basis for Carbapenem Hydrolysis by Class A β-Lactamases: A Combined Investigation using Crystallography and Simulations
Fátima Fonseca *†‡, Ewa I. Chudyk §, Marc W. van der Kamp §, António Correia ‡, Adrian J. Mulholland *§, and James Spencer *†
Carbapenems are the most potent β-lactam antibiotics and key drugs for treating infections by Gram-negative bacteria. In such organisms, β-lactam resistance arises principally from β-lactamase production. Although carbapenems escape the activity of most β-lactamases, due in the class A enzymes to slow deacylation of the covalent acylenzyme intermediate, carbapenem-hydrolyzing class A β-lactamases are now disseminating in clinically relevant bacteria. The reasons why carbapenems are substrates for these enzymes, but inhibit other class A β-lactamases, remain to be fully established. Here, we present crystal structures of the class A carbapenemase SFC-1 from Serratia fonticola and of complexes of its Ser70 Ala (Michaelis) and Glu166 Ala (acylenzyme) mutants with the carbapenem meropenem. These are the first crystal structures of carbapenem complexes of a class A carbapenemase. Our data reveal that, in the SFC-1 acylenzyme complex, the meropenem 6α-1R-hydroxyethyl group interacts with Asn132, but not with the deacylating water molecule. Molecular dynamics simulations indicate that this mode of binding occurs in both the Michaelis and acylenzyme complexes of wild-type SFC-1. In carbapenem-inhibited class A β-lactamases, it is proposed that the deacylating water molecule is deactivated by interaction with the carbapenem 6α-1R-hydroxyethyl substituent. Structural comparisons with such enzymes suggest that in SFC-1 subtle repositioning of key residues (Ser70, Ser130, Asn132 and Asn170) enlarges the active site, permitting rotation of the carbapenem 6α-1R-hydroxyethyl group and abolishing this contact. Our data show that SFC-1, and by implication other such carbapenem-hydrolyzing enzymes, uses Asn132 to orient bound carbapenems for efficient deacylation and prevent their interaction with the deacylating water molecule.
