Biochemical analysis of the ceftazidime-hydrolysing extended-spectrum β-lactamase CTX-M-15 and of its structurally related β-lactamase CTX-M-3
Biochemical analysis of the ceftazidime-hydrolysing extended-spectrum β-lactamase CTX-M-15 and of its structurally related β-lactamase CTX-M-3
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DOI：
10.1093/jac/dkf240
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发表时间：
2002-12-01
影响因子：
5.2
通讯作者：
Nordmann, P
中科院分区：
文献类型：
--
作者：
Poirel, L;Gniadkowski, M;Nordmann, P
与大多数CTX-M型酶不同，超广谱β-内酰胺酶CTX-M-15对头孢他啶具有耐药性。从纯化的CTX-M-15和CTX-M-3，根据A类β-内酰胺酶的Ambler编号，测定了不同氨基酸取代的单一氨基酸Asp-240和Gly的动力学参数。CTX-M-15和CTX-M-3的相对分子质量接近29 kDa，等电点分别为8.9和8.4。与CTX-M-3相比，CTX-M-15对β-内酰胺的亲和力较高(K-m值较低)，但催化效率(k(CAT)/K-m值)因底物不同而不同。只有CTX-M-15对头孢他啶有较高的催化效率。克拉维酸和他唑巴坦对两种酶均有较好的抑制作用。除头孢他啶外，表达相同遗传背景的克隆β-内酰胺酶基因的大肠埃希菌对β-内酰胺类抗生素的MIC相似。这项工作强调了这样一个事实，即一些CTX-M酶可能水解头孢他啶，从而在肠杆菌科对这种超广谱头孢菌素产生耐药性。
The extended-spectrum beta-lactamase CTX-M-15 confers resistance to ceftazidime, unlike the majority of CTX-M-type enzymes. Kinetic parameters were determined from purified CTX-M-15 and CTX-M-3, which differ by the single amino acid substitution Asp-240 to Gly, according to the Ambler numbering of class A beta-lactamases. Relative molecular masses of CTX-M-15 and CTX-M-3 were similar to29 kDa and pI values were 8.9 and 8.4, respectively. CTX-M-15 had higher affinities for beta-lactams (lower K-m values) than those of CTX-M-3 but catalytic efficiency (k(cat)/K-m values) was variable depending on the beta-lactam substrate. Only CTX-M-15 showed a measurable catalytic efficiency for ceftazidime. Clavulanic acid and tazobactam were good inhibitors of both enzymes. MICs of beta-lactams for Escherichia coli reference strains expressing cloned beta-lactamase genes in the same genetic background were similar except for ceftazidime. This work underlines the fact that some CTX-M enzymes may hydrolyse ceftazidime and thus confer resistance to this expanded-spectrum cephalosporin in Enterobacteriaceae.