Kawakami Toru
Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka, 565-0871, Japan,
Top Curr Chem. 2015;362:107-35. doi: 10.1007/128_2014_575.
In chemical protein synthesis, peptide building blocks are prepared by solid-phase peptide synthesis (SPPS), and then connected by chemical ligation methods. The peptide thioester is one of key building blocks used in chemical protein synthesis, and improvements in the Fmoc SPPS procedure for preparing such thioesters would be highly desirable. In this review we focus on a method for peptide thioester synthesis based on the use of an intramolecular N to S acyl shift reaction as a key reaction. Amide and thioester forms at the thiol-containing residue are in equilibrium as a result of a reversible intramolecular acyl shift, which is detectable by 13C NMR. The amide form is favored under neutral conditions, while the thioester predominates under acidic conditions. Thiol auxiliaries can be employed to facilitate the formation of a thioester from an amide via an intramolecular N-S acyl shift, and the peptide thioester is formed after intermolecular transthioesterification in the presence of excess amounts of thiols. Even under neutral conditions, thiol auxiliary-containing peptides can be ligated with a cysteinyl peptide via an intramolecular N-S acyl shift, followed by native chemical ligation (NCL) in a one-pot reaction. These procedures can be applied to the chemical synthesis of proteins which are post-translationally modified.
在化学蛋白质合成中，肽构建块通过固相肽合成（SPPS）制备，然后通过化学连接方法连接。肽硫酯是化学蛋白质合成中使用的关键构建块之一，因此改进用于制备此类硫酯的Fmoc SPPS程序将非常有必要。在本综述中，我们重点关注一种基于使用分子内N到S酰基转移反应作为关键反应的肽硫酯合成方法。由于可逆的分子内酰基转移，含硫醇残基处的酰胺和硫酯形式处于平衡状态，这可以通过13C NMR检测到。酰胺形式在中性条件下占优势，而硫酯在酸性条件下占主导地位。硫醇助剂可用于通过分子内N-S酰基转移促进从酰胺形成硫酯，并且在存在过量硫醇的情况下通过分子间硫酯交换反应形成肽硫酯。即使在中性条件下，含硫醇助剂的肽也可以通过分子内N-S酰基转移与半胱氨酰肽连接，然后在一锅反应中进行天然化学连接（NCL）。这些程序可应用于翻译后修饰蛋白质的化学合成。
