Beyond Making Thiazolines and Oxazolines: Expanding the Enzymatic Repertoire to incorporate other 5- and 6-membered heterocyclic rings in peptides

他的项目旨在开发一种新颖、高效和环保的酶促方法，以商业上可行的成本将一系列杂环纳入环状肽中。这些修饰将：1)通过稳定肽的二级结构，提高活性、受体结合亲和力和选择性；2)增强对代谢和消化酶的稳定性，从而提高口服生物利用度；3)通过减少氢键供体（HBDs）的数量来改善细胞通透性。我们以前报道过利用酶将半胱氨酸、丝氨酸和苏氨酸脱水环化，将噻唑啉和恶唑啉结合到环肽中。这些酶来源于核糖体合成和翻译后修饰肽（RiPPs）的生物合成途径，其中前体肽由核糖体合成并由一组加工酶定制以获得修饰的环肽。前体肽包含一个被称为“先导”的杂环酶识别的序列，通常随后是蛋白酶裂解信号和被加工成最终产物（核心肽）的序列。识别和加工位点的遥远分离使这些酶对底物序列的变化具有高度的耐受性，并具有生物技术应用的吸引力。我们已经研究了其中一些酶的结构和机制，并设计了一种与底物识别序列融合的酶，这样它就可以处理独立的核心序列。我们的目标是运用我们的专业知识为我们的工具箱添加新的酶，并探索亲核侧链的化学灵活性，以便在环肽中加入其他5和6元杂环。

his project aims at developing a novel, efficient and eco-friendly enzymatic approach to incorporate a range of heterocyclic rings in cyclic peptides at a commercially viable cost. These modifications will: 1) improve activity, receptor binding affinity and selectivity by stabilizing the peptide secondary structure; 2) enhance the stability against metabolic and digestive enzymes thus improve oral bioavailability and 3) improve cellular permeability by decreasing the number of hydrogen bond donors (HBDs). We previously reported the use of enzymes to incorporate thiazolines and oxazolines in cyclic peptides by dehydrative cyclization of cysteine, serine and threonine. These enzymes were derived from the biosynthetic pathways of the ribosomally synthesized and posttranslationally modified peptides (RiPPs) in which a precursor peptide is ribosomally-synthesised and tailored by a set of processing enzymes to give the modified cyclic peptide. The precursor peptide contains a sequence recognised by the heterocyclase called "leader", typically followed by a protease cleavage signal and the sequence to be processed to a final product (the core peptide). The distant separation of the recognition and processing sites makes these enzymes highly tolerant to variations in substrate sequence and appealing for biotechnological applications. We have studied the structure and mechanism of some of these enzymes and engineered an enzyme which is fused with its substrate recognition sequence so it can process stand-alone core sequences. We aim to apply our expertise to add new enzymes to our toolbox and to explore the chemical flexibility of the nucleophilic side chain to enable the incorporation of other 5 and 6 membered heterocycles in cyclic peptides.