Linear phycoxyloglucan with oligo-xylose domains in the green seaweed Ulva : a unique hemicellulose

作者：Marie N. Rapin, Lorna Murray, John H. Bothwell, Ian H. Sadler, Stephen C. Fry · 发表于：Annals of Botany · 年份：2026 · DOI：10.1093/aob/mcag195 · 研究领域：Seaweed-derived Bioactive Compounds、Marine and coastal plant biology、Polysaccharides and Plant Cell Walls

BACKGROUND AND AIMS: The chlorophycean seaweed genus Ulva (sea lettuce and relatives) possesses cellulose and cell-wall-matrix polysaccharides operationally classified as 'pectin-like' (hot-water-extractable anionic ulvans and glucuronans) and hemicelluloses. As Ulva is only distantly related to streptophytes (land-plants plus charophytic algae), their wall polysaccharides are likely to diverge significantly. We therefore explored the little-known structure and properties of Ulva hemicellulose. METHODS: Hemicellulose-b was alkali-extracted from hot-oxalate-pretreated U. linza alcohol-insoluble residue, then digested with endo-β-xylanase, Driselase or endo-cellulase, yielding several oligosaccharides. These were separated by size on gel-permeation and preparative paper chromatography. Oligosaccharides were dissected by acid hydrolysis, glycosidase digestion and alkaline peeling; products were analysed by thin-layer chromatography. Purified oligosaccharides were also characterised by NMR spectroscopy. KEY RESULTS: Thirteen di- to pentasaccharides were purified. On acid hydrolysis, they yielded only xylose (Xyl) and/or glucose (Glc). Each was digestible by either β-xylosidase or β-glucosidase, identifying the non-reducing terminus as β-Xyl or β-Glc respectively. The rate of alkaline peeling, which attacks progressively from the reducing terminus, indicated (1→4)-linkages; in each case the smallest peeling product (i.e., originally the non-reducing terminus) was either Xyl or Glc...