Cahill Samuel T, Tarhonskaya Hanna, Rydzik Anna M, Flashman Emily, McDonough Michael A, Schofield Christopher J, Brem Jürgen
Chemistry Research Laboratory, Oxford, United Kingdom.
Chemistry Research Laboratory, Oxford, United Kingdom.
J Inorg Biochem. 2016 Oct;163:185-193. doi: 10.1016/j.jinorgbio.2016.07.013. Epub 2016 Jul 26.
Metallo-β-lactamases (MBLs) catalyse the hydrolysis of almost all β-lactam antibacterials including the latest generation carbapenems and are a growing worldwide clinical problem. It is proposed that MBLs employ one or two zinc ion cofactors in vivo. Isolated MBLs are reported to use transition metal ions other than zinc, including copper, cadmium and manganese, with iron ions being a notable exception. We report kinetic and biophysical studies with the di-iron(II)-substituted metallo-β-lactamase II from Bacillus cereus (di-Fe(II) BcII) and the clinically relevant B1 subclass Verona integron-encoded metallo-β-lactamase 2 (di-Fe(II) VIM-2). The results reveal that MBLs can employ ferrous iron in catalysis, but with altered kinetic and inhibition profiles compared to the zinc enzymes. A crystal structure of di-Fe(II) BcII reveals only small overall changes in the active site compared to the di-Zn(II) enzyme including retention of the di-metal bridging water; however, the positions of the metal ions are altered in the di-Fe(II) compared to the di-Zn(II) structure. Stopped-flow analyses reveal that the mechanism of nitrocefin hydrolysis by both di-Fe(II) BcII and di-Fe(II) VIM-2 is altered compared to the di-Zn(II) enzymes. Notably, given that the MBLs are the subject of current medicinal chemistry efforts, the results raise the possibility the Fe(II)-substituted MBLs may be of clinical relevance under conditions of low zinc availability, and reveal potential variation in inhibitor activity against the differently metallated MBLs.
金属β-内酰胺酶（MBLs）可催化几乎所有β-内酰胺类抗菌药物的水解，包括最新一代的碳青霉烯类，这在全球范围内正逐渐成为一个临床问题。有人提出，MBLs在体内使用一个或两个锌离子辅因子。据报道，分离出的MBLs会使用除锌以外的过渡金属离子，包括铜、镉和锰，铁离子是一个显著的例外。我们报告了对蜡样芽孢杆菌的二价铁取代金属β-内酰胺酶II（二价铁BcII）和临床相关的B1亚类维罗纳整合子编码金属β-内酰胺酶2（二价铁VIM-2）的动力学和生物物理研究。结果表明，MBLs可以在催化过程中使用亚铁离子，但与锌酶相比，其动力学和抑制特性有所改变。二价铁BcII的晶体结构显示，与二价锌酶相比，活性位点仅发生了微小的整体变化，包括双金属桥连水的保留；然而，与二价锌结构相比，二价铁结构中金属离子的位置发生了改变。停流分析表明，与二价锌酶相比，二价铁BcII和二价铁VIM-2水解硝基头孢菌素的机制发生了改变。值得注意的是，鉴于MBLs是当前药物化学研究的对象, 这些结果增加了在低锌可用性条件下，二价铁取代的MBLs可能具有临床相关性的可能性，并揭示了针对不同金属化MBLs的抑制剂活性的潜在差异。
