Residues distal to the active site contribute to enhanced catalytic activity of variant and hybrid β-lactamases derived from CTX-M-14 and CTX-M-15

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

18 Scopus Citations
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Author(s)

  • Dandan He
  • Jiachi Chiou
  • Zhenling Zeng
  • Lanping Liu
  • Xiaojie Chen
  • Li Zeng
  • Edward Wai Chi Chan
  • Jian-Hua Liu

Detail(s)

Original languageEnglish
Pages (from-to)5976-5983
Journal / PublicationAntimicrobial Agents and Chemotherapy
Volume59
Issue number10
Online published18 Sep 2015
Publication statusPublished - Oct 2015
Externally publishedYes

Abstract

A variety of CTX-M-type extended-spectrum β-lactamases (ESBLs), including hybrid ones, have been reported in China that are uncommon elsewhere. To better characterize the substrate profiles and enzymatic mechanisms of these enzymes, we performed comparative kinetic analyses of both parental and hybrid CTX-M enzymes, including CTX-M-15, -132, -123, -64, -14 and -55, that are known to confer variable levels of β-lactam resistance in the host strains. All tested enzymes were susceptible to serine β-lactamase inhibitors, with sulbactam exhibiting the weakest inhibitory effects. CTX-M-55, which differs from CTX-M-15 by one substitution, A77V, displayed enhanced catalytic activity (kcat/Km) against expanded-spectrum cephalosporins (ESCs). CTX-M-55 exhibits higher structure stability, most likely by forming hydrophobic interactions between A77V and various key residues in different helices, thereby stabilizing the core architecture of the helix cluster, and indirectly contributes to a more stable active site conformation, which in turn shows higher catalytic efficiency and is more tolerant to temperature change. Analyses of the hybrids and their parental prototypes showed that evolution from CTX-M-15 to CTX-M-132, CTX-M-123, and CTX-M-64, characterized by gradual enhancement of catalytic activity to ESCs, was attributed to introduction of different substitutions to amino acids distal to the active site of CTX-M-15. Similarly, the increased hydrolytic activities against cephalosporins and sensitivity to β-lactamase inhibitors, clavulanic acid and sulbactam, of CTX-M-64 were partly due to the amino acids that were different from CTX-M-14 and located at both the C and N termini of CTX-M-64. These data indicate that residues distal to the active site of CTX-Ms contributed to their enhanced catalytic activities to ESCs.

Citation Format(s)

Residues distal to the active site contribute to enhanced catalytic activity of variant and hybrid β-lactamases derived from CTX-M-14 and CTX-M-15. / He, Dandan; Chiou, Jiachi; Zeng, Zhenling; Liu, Lanping; Chen, Xiaojie; Zeng, Li; Chan, Edward Wai Chi; Liu, Jian-Hua; Chen, Sheng.

In: Antimicrobial Agents and Chemotherapy, Vol. 59, No. 10, 10.2015, p. 5976-5983.

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review