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The model polysaccharide potato galactan is actually a mixture of different polysaccharides
Zhangkai Feng1, Zhiying Lin1, Huazhi Tang1
1Engineering Research Center of Glycoconjugates Ministry of Education, Jilin Province Key Laboratory of Chemistry and Biology of Changbai Mountain Natural Drugs, School of Life Sciences, Northeast Normal University, Changchun 130024, PR China.
Abstract:
Commercially-supplied potato galactan (PG) is widely used as a model polysaccharide in various bioactivity studies. However, results using this galactan are not always consistent with the stated composition. Here, we assessed its composition by fractionating this commercial PG and purified its primary components: PG-A, PG-B and PG-Cp with weight-averaged molecular weights of 430, 93, and 11.3 kDa, respectively. PG-Cp consists of free β-1,4-galactan chains, whereas PG-A and PG-B are type I rhamnogalacturonans with long β-1,4-galactan side chains of up to 80 Gal residues and short β-1,4-galactan side chains of 0 to 3 Gal residues that display a "trees in lawn" pattern. Structures of these polysaccharides correlate well with their activities in terms of galectin-3 binding and gut bacterial growth assays. Our study clarifies the confusion related to commercial PG, with purified fractions serving as better model polysaccharides in bioactivity investigations.