AbstractThe O‐acetylation of the muramic acid residues in peptidoglycan (PG) is a modification that protects the bacteria from lysis due to the action of lysozyme. In Gram‐negative bacteria, deacetylation is required to allow lytic transglycosylases to promote PG cleavage during cell growth and division. This deacetylation is catalyzed by O‐acetylpeptidoglycan esterase (Ape) which is a serine esterase and employs covalent catalysis via a serine‐linked acyl enzyme intermediate. Loss of Ape activity affects the size and shape of bacteria and dramatically reduces virulence. In this work, we report the first rationally designed aldehyde‐based inhibitors of Ape from Campylobacter jejuni. The most potent of these acts as a competitive inhibitor with a Ki value of 13 μM. We suspect that the inhibitors are forming adducts with the active site serine that closely mimic the tetrahedral intermediate of the normal catalytic cycle. Support for this notion is found in the observation that reduction of the aldehyde to an alcohol effectively abolishes the inhibition.
摘要肽聚糖(PG)中μramic酸残基的O-乙酰化是一种修饰,可保护细菌不因溶菌酶的作用而溶解。在革兰氏阴性细菌中,需要进行脱乙酰化,以使溶菌性转糖基化酶在细胞生长和分裂过程中促进肽聚糖的裂解。这种去乙酰化作用由 O-乙酰肽聚糖酯酶(Ape)催化,Ape 是一种丝氨酸酯酶,通过丝氨酸连接的酰基酶中间体进行共价催化。Ape 活性的丧失会影响细菌的大小和形状,并显著降低毒力。在这项工作中,我们报告了首个合理设计的空肠弯曲杆菌 Ape 醛基抑制剂。其中最有效的抑制剂是 Ki 值为 13 μM 的竞争性抑制剂。我们怀疑抑制剂正在与活性位点丝氨酸形成加合物,这种加合物与正常催化循环的四面体中间体非常相似。将醛还原成醇可有效地消除抑制作用,这一观察结果支持了上述观点。