Swarén P, Maveyraud L, Raquet X, Cabantous S, Duez C, Pédelacq J D, Mariotte-Boyer S, Mourey L, Labia R, Nicolas-Chanoine M H, Nordmann P, Frère J M, Samama J P
Groupe de Cristallographie Biologique, Institut de Pharmacologie et de Biologie Structurale, UPR 9062 CNRS, 205 route de Narbonne, F-31077 Toulouse CEDEX, France.
J Biol Chem. 1998 Oct 9;273(41):26714-21. doi: 10.1074/jbc.273.41.26714.
The treatment of infectious diseases by penicillin and cephalosporin antibiotics is continuously challenged by the emergence and the dissemination of the numerous TEM and SHV mutant beta-lactamases with extended substrate profiles. These class A beta-lactamases nevertheless remain inefficient against carbapenems, the most effective antibiotics against clinically relevant pathogens. A new member of this enzyme class, NMC-A, was recently reported to hydrolyze at high rates, and hence destroy, all known beta-lactam antibiotics, including carbapenems and cephamycins. The crystal structure of NMC-A was solved to 1.64-A resolution, and reveals modifications in the topology of the substrate-binding site. While preserving the geometry of the essential catalytic residues, the active site of the enzyme presents a disulfide bridge between residues 69 and 238, and certain other structural differences compared with the other beta-lactamases. These unusual features in class A beta-lactamases involve amino acids that participate in enzyme-substrate interactions, which suggested that these structural factors should be related to the very broad substrate specificity of this enzyme. The comparison of the NMC-A structure with those of other class A enzymes and enzyme-ligand complexes, indicated that the position of Asn-132 in NMC-A provides critical additional space in the region of the protein where the poorer substrates for class A beta-lactamases, such as cephamycins and carbapenems, need to be accommodated.
青霉素和头孢菌素类抗生素对传染病的治疗不断受到众多具有扩展底物谱的TEM和SHV突变β-内酰胺酶出现和传播的挑战。然而，这些A类β-内酰胺酶对碳青霉烯类抗生素仍然无效，而碳青霉烯类抗生素是对抗临床相关病原体最有效的抗生素。最近报道了该酶类的一个新成员NMC-A，它能高速水解并因此破坏所有已知的β-内酰胺抗生素，包括碳青霉烯类抗生素和头孢霉素。NMC-A的晶体结构解析分辨率达到1.64 Å，揭示了底物结合位点拓扑结构的改变。在保留关键催化残基几何形状的同时，该酶的活性位点在69位和238位残基之间存在一个二硫键，并且与其他β-内酰胺酶相比还有某些其他结构差异。A类β-内酰胺酶中的这些不寻常特征涉及参与酶-底物相互作用的氨基酸，这表明这些结构因素应该与该酶非常广泛的底物特异性有关。将NMC-A的结构与其他A类酶和酶-配体复合物的结构进行比较表明, NMC-A中Asn-132的位置在该蛋白质区域提供了关键的额外空间，在该区域需要容纳A类β-内酰胺酶较差的底物，如头孢霉素和碳青霉烯类抗生素。
