Lohans Christopher T, Wang David Y, Jorgensen Christian, Cahill Samuel T, Clifton Ian J, McDonough Michael A, Oswin Henry P, Spencer James, Domene Carmen, Claridge Timothy D W, Brem Jürgen, Schofield Christopher J
Department of Chemistry, University of Oxford, Oxford, OX1 3TA, UK.
Department of Chemistry, King's College London, London, SE1 1DB, UK.
Org Biomol Chem. 2017 Jul 19;15(28):6024-6032. doi: 10.1039/c7ob01514c.
The class D (OXA) serine β-lactamases are a major cause of resistance to β-lactam antibiotics. The class D enzymes are unique amongst β-lactamases because they have a carbamylated lysine that acts as a general acid/base in catalysis. Previous crystallographic studies led to the proposal that β-lactamase inhibitor avibactam targets OXA enzymes in part by promoting decarbamylation. Similarly, halide ions are proposed to inhibit OXA enzymes via decarbamylation. NMR analyses, in which the carbamylated lysines of OXA-10, -23 and -48 were C-labelled, indicate that reaction with avibactam does not ablate lysine carbamylation in solution. While halide ions did not decarbamylate the C-labelled OXA enzymes in the absence of substrate or inhibitor, avibactam-treated OXA enzymes were susceptible to decarbamylation mediated by halide ions, suggesting halide ions may inhibit OXA enzymes by promoting decarbamylation of acyl-enzyme complex. Crystal structures of the OXA-10 avibactam complex were obtained with bromide, iodide, and sodium ions bound between Trp-154 and Lys-70. Structures were also obtained wherein bromide and iodide ions occupy the position expected for the 'hydrolytic water' molecule. In contrast with some solution studies, Lys-70 was decarbamylated in these structures. These results reveal clear differences between crystallographic and solution studies on the interaction of class D β-lactamases with avibactam and halides, and demonstrate the utility of C-NMR for studying lysine carbamylation in solution.
D类（OXA）丝氨酸β-内酰胺酶是对β-内酰胺抗生素耐药的主要原因。D类酶在β-内酰胺酶中独一无二，因为它们有一个氨甲酰化赖氨酸，在催化过程中充当一般酸碱。先前的晶体学研究表明，β-内酰胺酶抑制剂阿维巴坦部分通过促进脱氨甲酰化作用靶向OXA酶。同样，有人提出卤离子通过脱氨甲酰化作用抑制OXA酶。核磁共振分析表明，用碳-13标记OXA-10、-23和-48的氨甲酰化赖氨酸，与阿维巴坦的反应并不会消除溶液中赖氨酸的氨甲酰化。虽然在没有底物或抑制剂的情况下卤离子不会使碳-13标记的OXA酶脱氨甲酰化，但经阿维巴坦处理的OXA酶易受卤离子介导的脱氨甲酰化作用影响，这表明卤离子可能通过促进酰基酶复合物的脱氨甲酰化作用来抑制OXA酶。获得了OXA-10与阿维巴坦复合物的晶体结构，其中溴离子、碘离子和钠离子结合在色氨酸-154和赖氨酸-70之间。还获得了溴离子和碘离子占据“水解水”分子预期位置结构。与一些溶液研究结果相反，在这些结构中赖氨酸-70发生了脱氨甲酰化。这些结果揭示了关于D类β-内酰胺酶与阿维巴坦和卤化物相互作用的晶体学研究和溶液研究之间的明显差异，并证明了碳-13核磁共振在研究溶液中赖氨酸氨甲酰化方面的实用性。
需注意，原文中“NMR analyses, in which the carbamylated lysines of OXA-10, -23 and -48 were C-labelled”这里推测应该是“13C-labelled”，按照推测进行了翻译，若实际不是这样，请根据正确信息调整。
