Medical Biology Department, Kocaeli University Medical School , Kocaeli , Turkey.
J Enzyme Inhib Med Chem. 2013 Oct;28(5):990-6. doi: 10.3109/14756366.2012.702343. Epub 2012 Jul 30.
Isolation and characterization of OXA-162, a novel variant of OXA-48.
Klebsiella pneumoniae isolate with decreased susceptibility to carbapenems was recovered from a Turkish patient. This study aimed at characterizing the carbapenem resistance determinants of this isolate.
Antibiotic susceptibility tests, analytic isoelectric focusing (IEF), cloning and sequencing were performed. Cloned β-lactamase was purified by means of preparative gel electrophoresis and the kinetic constants were determined under initial rate conditions.
The identified bla(OXA-162) gene was located on a ca. 45-kb plasmid carrying a transposon consisted of two IS1999-2 elements. OXA-162 differed from OXA-48 by a single amino acid substitution (Thr213Ala) which increased the catalytic efficiency (k(cat)/K(M)) of OXA-162 towards imipenem and meropenem. Also this substitution caused a gain of hydrolysis ability towards doripenem. Analysis of OXA-162 model implied that the amino acid change might generate an extension in the opening of the substrate entry site and might cause extended hydrolytic activity towards imipenem, meropenem and doripenem.
OXA-162, a derivative of OXA-48 has enhanced catalytic properties.
OXA-162 是 OXA-48 的一种新型变体，其被分离并进行了特性分析。
从一名土耳其患者体内分离出对碳青霉烯类药物敏感性降低的肺炎克雷伯菌。本研究旨在对该分离株的碳青霉烯类药物耐药决定因子进行特性分析。
进行抗生素敏感性试验、分析等电聚焦（IEF）、克隆和测序。通过制备性凝胶电泳对克隆的β-内酰胺酶进行纯化，并在初始速率条件下测定动力学常数。
鉴定的 bla（OXA-162）基因位于一个约 45kb 的质粒上，该质粒携带有一个由两个 IS1999-2 元件组成的转座子。与 OXA-48 相比，OXA-162 仅发生了一个氨基酸取代（Thr213Ala），这增加了 OXA-162 对亚胺培南和美罗培南的催化效率（kcat/KM）。此外，这种取代还导致了对多利培南的水解能力增强。对 OXA-162 模型的分析表明，该氨基酸变化可能会导致底物进入位点的开口扩大，并可能导致对亚胺培南、美罗培南和多利培南的水解活性增强。
OXA-162 是 OXA-48 的衍生物，具有增强的催化特性。
