Son Seung-U, Lee Sue Jung, Choi Eun Hye, Shin Kwang-Soon
Department of Food Science and Biotechnology, Kyonggi University, Suwon 16227, Republic of Korea; Transdisciplinary Major in Learning Health System, Department of Integrated Biomedical and Life Science, Graduate School, Korea University, Seoul 02841, Republic of Korea.
KIST Gangneung Institute of Natural Products, Korea Institute of Science and Technology (KIST), Gangneung 25451, Republic of Korea.
Int J Biol Macromol. 2022 Jun 1;209(Pt A):923-934. doi: 10.1016/j.ijbiomac.2022.04.045. Epub 2022 Apr 18.
Determining the structure of REPI, an immunostimulatory polysaccharide fraction from radish leaves, is an important health objective. Herein, we show that REP-I contains nine different monosaccharides, including GalA (22.2%), Gal (32.6%), Ara (27.5%), and Rha (10.2%) as main sugars. REP-I was also reacted with β-glucosyl Yariv reagent (29.8%), suggesting the presence of the arabino-β-3,6-galactan. Furthermore, methylated-product analysis revealed that REP-I contains 13 different glycosyl linkages, including 4-linked GalpA (21.0%), 2,4-linked Rhap (7.0%), 4-linked Galp (5.8%), 5-linked Araf (10.1%), and 3,6-linked Galp (7.9%), which are characteristic of RG-I. Microstructural information was obtained by sequential degradation using four linkage-specific glycosylases and β-elimination, with fragments analyzed on the basis of sugar composition, methylation, and MS/MS spectra. The results show that the immunostimulatory activity of REP-I is possibly due to the structure of RG-I, which is composed of a main chain with repeating [→2)-Rhap-(1 → 4)-GalpA-(1→] linkage units and three side-chains: a branched α(1 → 5)arabinan, a β(1 → 4)galactan, and arabino-β-3,6-galactan, which are branched at the C(O)4 position of each Rha residue in the REP-I main chain.
确定萝卜叶免疫刺激多糖组分REP-I的结构是一项重要的健康目标。在此，我们表明REP-I含有九种不同的单糖，其中主要糖类包括半乳糖醛酸（GalA，22.2%）、半乳糖（Gal，32.6%）、阿拉伯糖（Ara，27.5%）和鼠李糖（Rha，10.2%）。REP-I还与β-葡萄糖基Yariv试剂发生反应（29.8%），表明存在阿拉伯糖基-β-3,6-半乳聚糖。此外，甲基化产物分析表明REP-I含有13种不同的糖基连接，包括4-连接的半乳糖醛酸（GalpA，21.0%）、2,4-连接的鼠李糖（Rhap，7.0%）、4-连接的半乳糖（Galp，5.8%）、5-连接的阿拉伯糖（Araf，10.1%）和3,6-连接的半乳糖（Galp，7.9%），这些都是鼠李糖半乳糖醛酸聚糖-I（RG-I）的特征。通过使用四种连接特异性糖基化酶进行顺序降解和β-消除获得微观结构信息，并根据糖组成、甲基化和MS/MS光谱对片段进行分析。结果表明，REP-I的免疫刺激活性可能归因于RG-I的结构，其由具有重复[→2)-Rhap-(1→4)-GalpA-(1→]连接单元的主链和三个侧链组成：一个分支的α(1→5)阿拉伯聚糖、一个β(1→4)半乳聚糖和阿拉伯糖基-β-3,6-半乳聚糖，它们在REP-I主链中每个Rha残基的C(O)4位置分支。
