新加坡南洋理工大学Chuan-Fa Liu团队报道了一种多功能非天然氨基酸，Nγ-羟基天冬酰胺，是天冬酰胺基肽连接酶良好的P1底物。相关研究成果于2021年8月15日发表于国际顶尖学术期刊《德国应用化学》。

肽基天冬酰胺基连接酶（PAL）是肽大环化的有力工具。

该文中，研究人员报告Asn的一种衍生物，即Nγ-羟基天冬酰胺或Asn（OH），是PAL的一种非天然P1底物。利用Asn（OH）介导的环化反应，研究人员制备了环肽作为新的基质金属蛋白酶2（MMP2）抑制剂，显示Asn（OH）的羟肟酸部分为关键药效团。其中最强的环肽17（KI=2.8±0.5 nM）构建在猕猴θ防御素-1的超稳定四环支架上。环化肽中的Asn（OH）残基也可轻易氧化为Asp。

利用该方法，研究人员合成了几种具有生物活性的含Asp的环肽（MCoTI II、kB2、SFTI和整合素靶向RGD肽），由于P1 Asp底物的不利动力学，它们是PAL催化环化的困难靶点。

该研究表明，底物工程是扩大PAL连接在治疗性环肽合成中应用的有效策略。

附：英文原文

Title: Nγ-Hydroxyasparagine: a Multifunctional Unnatural Amino Acid That is a Good P1 Substrate of Asparaginyl Peptide Ligases

Author: Chuan-Fa Liu, Yiyin Xia, Janet To, Ning-Yu Chan, Side Hu, Heng Tai Liew, Seetharamsing Balamkundu, Xiaohong Zhang, Julien Lescar, Surajit Bhattacharjya, James P. Tam

Issue&Volume: 2021-08-15

Abstract: Peptidyl Asparaginyl Ligases (PALs) are powerful tools for peptide macrocyclization. Herein, we report that a derivative of Asn, namely  N  γ  -hydroxyl-asparagine or Asn(OH), is an unnatural P1 substrate of PALs. Using Asn(OH)-mediated cyclization, we prepared cyclic peptides as new matrix metalloproteinase 2 (MMP2) inhibitors displaying the hydroxamic acid moiety of Asn(OH) as the key pharmacophore. Cyclic peptide  17  , the most potent of these (K  i  = 2.8 ± 0.5 nM), was built on the hyper-stable tetracyclic scaffold of rhesus theta defensin-1. The Asn(OH) residue in the cyclized peptides can also be readily oxidized to Asp. Using this approach, we synthesized several bioactive Asp-containing cyclic peptides (MCoTI-II, kB2, SFTI, and integrin-targeting RGD peptides) that are otherwise difficult targets for PAL-catalyzed cyclization due to unfavorable kinetics of the P1-Asp substrates. This study demonstrates that substrate engineering is a useful strategy to expand the application of PAL ligation in the synthesis of therapeutic cyclic peptides.

DOI: 10.1002/anie.202108125

Source: https://onlinelibrary.wiley.com/doi/10.1002/anie.202108125