Zhu Qian, Nicolardi Simone, Wang Yuanguang, Liu Yasong, Xu Peng, Wang Jianjun, Zhu Dapeng, Yu Biao
State Key Laboratory of Chemical Biology, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai 200032, China.
Center for Proteomics and Metabolomics, Leiden University Medical Center, Leiden 2333ZA, The Netherlands.
Natl Sci Rev. 2024 Aug 23;11(10):nwae296. doi: 10.1093/nsr/nwae296. eCollection 2024 Oct.
Cold-adapted species are able to generate cryoprotective proteins and glycoproteins to prevent freezing damage. The [→4)--D-Man-(1→4)--D-Xyl-(1→] xylomannan from the Alaska beetle was disclosed by Walters and co-workers in 2009 as the first glycan-based antifreeze agent, which was later reported to be found in diverse taxa. Here, we report the rapid synthesis of four types of xylomannans, including the proposed antifreeze xylomannan up to a 64-mer (Type I), the regioisomeric [→3)--D-Man-(1→4)--D-Xyl-(1→] 16-mer (Type II), the diastereomeric [→4)--L-Man-(1→4)--D-Xyl-(1→] 16-mer (Type III) and the block-wise [→4)--D-Man-(1→] [→4)--D-Xyl-(1→] 32-mer (Type IV), by employing a strategic iterative exponential glycan growth (IEGG) process. The nuclear magnetic resonance spectral data of the alleged natural xylomannan are in accordance only to those of the block-wise Type IV glycan and none of these synthetic xylomannans has been found to be capable of inducing thermal hysteresis. These results disprove the previous reports about the natural occurrence of antifreeze xylomannans.
冷适应物种能够产生抗冻蛋白和糖蛋白以防止冻害。2009年，沃尔特斯及其同事公布了来自阿拉斯加甲虫的[→4)--D-甘露糖-(1→4)--D-木糖-(1→]木聚甘露糖，它是首个基于聚糖的抗冻剂，后来据报道在多种分类群中都有发现。在此，我们报告了通过采用策略性迭代指数聚糖生长（IEGG）过程快速合成四种类型的木聚甘露糖，包括高达64聚体的拟抗冻木聚甘露糖（I型）、区域异构体[→3)--D-甘露糖-(1→4)--D-木糖-(1→] 16聚体（II型）、非对映异构体[→4)--L-甘露糖-(1→4)--D-木糖-(1→] 16聚体（III型）和嵌段型[→4)--D-甘露糖-(1→] [→4)--D-木糖-(1→] 32聚体（IV型）。所谓天然木聚甘露糖的核磁共振光谱数据仅与嵌段型IV型聚糖的数据一致，并且未发现这些合成木聚甘露糖中的任何一种能够诱导热滞现象。这些结果反驳了先前关于抗冻木聚甘露糖天然存在的报道。
