Crystal structure and activity studies of the Mycobacterium tuberculosis β-lactamase reveal its critical role in resistance to β-lactam antibiotics
Crystal structure and activity studies of the Mycobacterium tuberculosis β-lactamase reveal its critical role in resistance to β-lactam antibiotics
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DOI：
10.1128/aac.00320-06
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发表时间：
2006-08-01
影响因子：
4.9
通讯作者：
Sacchettini, James C.
中科院分区：
文献类型：
--
作者：
Wang, Feng;Cassidy, Craig;Sacchettini, James C.
β-内酰胺抗生素在破坏革兰氏阳性和革兰氏阴性细菌中细菌细胞壁的合成方面非常有效。然而，它们对结核分枝杆菌是无效的，这是由于产生在M染色体上编码的β-内酰胺酶。结核病会降解这些抗生素。事实上，最近的研究已经证明，删除blaC基因，唯一的基因编码的β-内酰胺酶在M。结核病或抑制编码的酶导致对β-内酰胺抗生素的敏感性显著增加。本文介绍了M.结核病重组BlaC显示出广泛的特异性，具有几乎相等的青霉素酶和头孢噻吩酶活性。虽然克拉维汀是一种基于机制的高效A类β-内酰胺酶抑制剂（通常Ki < 0.1 μ M），但它是一种相对较差的M抑制剂。结核病BlaC（Ki = 2.4 μ M）。在1.7埃的分辨率下测定的酶的晶体结构表明，M。结核杆菌酶类似于其他A类β-内酰胺酶。然而，活性位点有几个不同的特征，如氨基酸取代N132 G、R164 A、R244 A和R276 E，这些特征解释了该酶的广泛特异性、相对较低的青霉素酶活性和对克拉维酶的抗性。
P-Lactam antibiotics are extremely effective in disrupting the synthesis of the bacterial cell wall in both gram-positive and gram-negative bacteria. However, they are ineffective against Mycobacterium tuberculosis, due to the production of a P-lactamase enzyme encoded on the chromosome of M. tuberculosis that degrades these antibiotics. Indeed, recent studies have demonstrated that deletion of the blaC gene, the only gene encoding a P-lactamase in M. tuberculosis, or inhibition of the encoded enzyme resulted in significantly increased sensitivity to P-lactam antibiotics. In this paper we present a biochemical and structural characterization of M. tuberculosis BlaC. Recombinant BlaC shows a broad range of specificity with almost equal penicillinase and cepholothinase activity. While clavulanate is a mechanism-based inhibitor to class A beta-lactamase with high potency (typically K-i < 0.1 mu M), it is a relatively poor inhibitor of the M. tuberculosis BlaC (K-i = 2.4 mu M). The crystal structure of the enzyme, determined at a resolution of 1.7 angstrom, shows that the overall fold of the M. tuberculosis enzyme is similar to other class A beta-lactamases. There are, however, several distinct features of the active site, such as the amino acid substitutions N132G, R164A, R244A, and R276E, that explain the broad specificity of the enzyme, relatively low penicillinase activity, and resistance to clavulanate.