Department of Biotechnological and Applied Clinical Sciences, University of L'Aquila, L'Aquila, Italy.
Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy.
Antimicrob Agents Chemother. 2022 Jun 21;66(6):e0240221. doi: 10.1128/aac.02402-21. Epub 2022 Jun 1.
KPC-53 enzyme is a natural KPC variant which showed a duplication of L167E168 residues in the Ω-loop structure. The gene was cloned both into pBC-SK and pET-24a vectors, and the recombinant plasmids were transferred by transformation in Escherichia coli competent cells to evaluate the antimicrobial susceptibility and to produce the enzyme. Compared to KPC-3, the KPC-53 was less stable and showed a dramatic reduction of and / versus several β-lactams, in particular carbapenems. Indeed, a 2,000-fold reduction was observed in the values of KPC-53 for imipenem and meropenem. Concerning inhibitors, KPC-53 was susceptible to tazobactam and clavulanic acid but maintained resistance to avibactam. The molecular modeling indicates that the L167E168 duplication in KPC-53 modifies the interactions between residues involved in the catalytic pocket, changing the flexibility of the Ω-loop, which is directly coupled with the catalytic properties of the KPC enzymes.
KPC-53 酶是一种天然的 KPC 变体，其在 Ω 环结构中显示出 L167E168 残基的重复。该基因被克隆到 pBC-SK 和 pET-24a 载体中，并通过转化大肠杆菌感受态细胞将重组质粒转移，以评估抗菌药物敏感性并产生酶。与 KPC-3 相比，KPC-53 不太稳定，并且对 和 / 几种β-内酰胺类药物（尤其是碳青霉烯类）的敏感性显著降低。事实上，KPC-53 对亚胺培南和美罗培南的 值降低了 2000 倍。关于抑制剂，KPC-53 对他唑巴坦和克拉维酸敏感，但对阿维巴坦保持耐药。分子建模表明，KPC-53 中的 L167E168 重复改变了参与催化口袋的残基之间的相互作用，改变了 Ω 环的灵活性，这与 KPC 酶的催化特性直接相关。
