Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
J Am Chem Soc. 2011 Jul 20;133(28):10748-51. doi: 10.1021/ja2040656. Epub 2011 Jun 27.
The β-lactams are the most important class of antibiotics in clinical use. Their lethal targets are the transpeptidase domains of penicillin binding proteins (PBPs), which catalyze the cross-linking of bacterial peptidoglycan (PG) during cell wall synthesis. The transpeptidation reaction occurs in two steps, the first being formation of a covalent enzyme intermediate and the second involving attack of an amine on this intermediate. Here we use defined PG substrates to dissect the individual steps catalyzed by a purified E. coli transpeptidase. We demonstrate that this transpeptidase accepts a set of structurally diverse D-amino acid substrates and incorporates them into PG fragments. These results provide new information on donor and acceptor requirements as well as a mechanistic basis for previous observations that noncanonical D-amino acids can be introduced into the bacterial cell wall.
β-内酰胺类抗生素是临床应用中最重要的一类抗生素。它们的致死靶标是青霉素结合蛋白（PBPs）的转肽酶结构域，该酶结构域在细胞壁合成过程中催化细菌肽聚糖（PG）的交联。转肽反应分两步进行，第一步是形成共价酶中间物，第二步是氨基攻击该中间物。在这里，我们使用定义明确的 PG 底物来剖析由纯化的大肠杆菌转肽酶催化的各个步骤。我们证明，该转肽酶可以接受一组结构多样的 D-氨基酸底物，并将其掺入 PG 片段中。这些结果提供了有关供体和受体要求的新信息，以及先前观察到的非典型 D-氨基酸可以引入细菌细胞壁的机制基础。
