Streamlined Chemoenzymatic Synthesis of Cyclic Peptides by Non-ribosomal Peptide Cyclases

Macrocyclization improves the pharmaceutical properties of peptides; however, regio- and chemoselective intramolecular cyclizations remain challenging. Here we developed a streamlined chemoenzymatic approach to synthesize cyclic peptides by exploiting non-ribosomal peptide (NRP) cyclases. Linear peptides linked to the resin through a C-terminal diol ester functionality are synthesized on a solid support, to circumvent the installation of leaving groups to the peptidic substrates in the liquid phase which often triggers undesirable epimerization. Cleavage of the resin-bound peptides yielded the diol esters with sufficient purity to be readily cyclized in a head-to-tail manner by SurE, a representative penicillin-binding protein-type thioesterase (PBP-type TE). Explorations of homologous wild-type enzymes as well as rational protein engineering have broadened the scope of the enzymatic macrolactamization. This method will potentially accelerate the exploitation of NRP cyclases as biocatalysts.

大环化可改善肽的药物特性；然而，区域选择性和化学选择性分子内环化仍然颇具挑战。在此，我们开发了一种简化的化学酶法，通过利用非核糖体肽（NRP）环化酶来合成环肽。在固相载体上合成通过C端二醇酯官能团连接到树脂上的线性肽，以避免在液相中将离去基团引入肽底物，因为这往往会引发不良的差向异构化。从树脂上裂解下来的肽得到的二醇酯纯度足以通过SurE（一种典型的青霉素结合蛋白型硫酯酶，即PBP型TE）以首尾相连的方式轻松环化。对同源野生型酶的探索以及合理的蛋白质工程拓宽了酶促大环内酰胺化的应用范围。该方法有望加速将NRP环化酶开发为生物催化剂。