Marine Biotechnology Research Division, Korea Institute of Ocean Science and Technology, Ansan, 426-744, Republic of Korea; Ocean Science and Technology School, Korea Maritime University, Pusan, 606-791, Republic of Korea; Department of Marine Biotechnology, University of Science and Technology, Daejeon, 305-333, Republic of Korea.
Proteins. 2013 Nov;81(11):2045-51. doi: 10.1002/prot.24334. Epub 2013 Aug 19.
EstU1 is a unique family VIII carboxylesterase that displays hydrolytic activity toward the amide bond of clinically used β-lactam antibiotics as well as the ester bond of p-nitrophenyl esters. EstU1 assumes a β-lactamase-like modular architecture and contains the residues Ser100, Lys103, and Tyr218, which correspond to the three catalytic residues (Ser64, Lys67, and Tyr150, respectively) of class C β-lactamases. The structure of the EstU1/cephalothin complex demonstrates that the active site of EstU1 is not ideally tailored to perform an efficient deacylation reaction during the hydrolysis of β-lactam antibiotics. This result explains the weak β-lactamase activity of EstU1 compared with class C β-lactamases. Finally, structural and sequential comparison of EstU1 with other family VIII carboxylesterases elucidates an operative molecular strategy used by family VIII carboxylesterases to extend their substrate spectrum.
EstU1 是一种独特的 VIII 族羧酸酯酶，对临床上使用的β-内酰胺类抗生素的酰胺键以及对硝基苯酯的酯键具有水解活性。EstU1 采用β-内酰胺酶样的模块化结构，包含残基 Ser100、Lys103 和 Tyr218，它们分别对应于 C 类β-内酰胺酶的三个催化残基（Ser64、Lys67 和 Tyr150）。EstU1/头孢菌素复合物的结构表明，EstU1 的活性位点在水解β-内酰胺类抗生素时不能很好地进行有效的去酰化反应。这一结果解释了 EstU1 与 C 类β-内酰胺酶相比β-内酰胺酶活性较弱的原因。最后，通过与其他 VIII 族羧酸酯酶的结构和序列比较，阐明了 VIII 族羧酸酯酶扩展其底物谱的有效分子策略。
