Department of Chemistry and Key Laboratory for Chemical Biology of Fujian Province, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, Fujian, China.
Key Laboratory of Bioorganic Phosphorus Chemistry and Chemical Biology (Ministry of Education), Department of Chemistry, Tsinghua University, Beijing, 100084, China.
Sci Rep. 2018 Jan 17;8(1):936. doi: 10.1038/s41598-018-19335-9.
Cyclic dipeptides, also known as 2,5-diketopiperazines (DKPs), represent the simplest peptides that were first completely characterized. DKPs can catalyze the chiral selection of reactions and are considered as peptide precursors. The origin of biochemical chirality and synthesis of peptides remains abstruse problem believed to be essential precondition to origin of life. Therefore, it is reasonable to believe that the DKPs could have played a key role in the origin of life. How the formation of the DKPs through the condensation of unprotected amino acids in simulated prebiotic conditions has been unclear. Herein, it was found that cyclo-Pro-Pro could be formed directly from unprotected proline in the aqueous solution of trimetaphosphate (Pm) under mild condition with the yield up to 97%. Other amino acids were found to form proline-containing DKPs under the same conditions in spite of lower yield. During the formation process of these DKPs, Pm promotes the formation of linear dipeptides in the first step of the mechanism. The above findings are helpful and significant for understanding the formation of DKPs in the process of chemical evolution of life.
环二肽，也称为 2,5-二酮哌嗪（DKP），代表了最早被完全描述的最简单的肽。DKP 可以催化反应的手性选择，被认为是肽的前体。生物化学手性的起源和肽的合成仍然是一个深奥的问题，被认为是生命起源的必要前提。因此，有理由相信 DKP 在生命起源中可能发挥了关键作用。在模拟原始条件下通过未保护的氨基酸缩合形成 DKP 的方式尚不清楚。本文发现，在温和条件下，环丙氨酸-脯氨酸可以直接从三偏磷酸盐（Pm）水溶液中的未保护脯氨酸中形成，产率高达 97%。在相同条件下，发现其他氨基酸也形成了含脯氨酸的 DKP，尽管产率较低。在这些 DKP 的形成过程中，Pm 在机制的第一步中促进了线性二肽的形成。这些发现有助于理解生命化学进化过程中环二肽的形成。
