Stegmayr John, Lepur Adriana, Kahl-Knutson Barbro, Aguilar-Moncayo Matilde, Klyosov Anatole A, Field Robert A, Oredsson Stina, Nilsson Ulf J, Leffler Hakon
From the Section MIG (Microbiology, Immunology, Glycobiology), Department of Laboratory Medicine, Lund University, 221 00 Lund, Sweden, the Department of Biology and
From the Section MIG (Microbiology, Immunology, Glycobiology), Department of Laboratory Medicine, Lund University, 221 00 Lund, Sweden.
J Biol Chem. 2016 Jun 17;291(25):13318-34. doi: 10.1074/jbc.M116.721464. Epub 2016 Apr 26.
Some complex plant-derived polysaccharides, such as modified citrus pectins and galactomannans, have been shown to have promising anti-inflammatory and anti-cancer effects. Most reports propose or claim that these effects are due to interaction of the polysaccharides with galectins because the polysaccharides contain galactose-containing side chains that might bind this class of lectin. However, their direct binding to and/or inhibition of the evolutionarily conserved galactoside-binding site of galectins has not been demonstrated. Using a well established fluorescence anisotropy assay, we tested the direct interaction of several such polysaccharides with physiological concentrations of a panel of galectins. The bioactive pectic samples tested were very poor inhibitors of the canonical galactoside-binding site for the tested galectins, with IC50 values >10 mg/ml for a few or in most cases no inhibitory activity at all. The galactomannan Davanat® was more active, albeit not a strong inhibitor (IC50 values ranging from 3 to 20 mg/ml depending on the galectin). Pure synthetic oligosaccharide fragments found in the side chains and backbone of pectins and galactomannans were additionally tested. The most commonly found galactan configuration in pectins had no inhibition of the galectins tested. Galactosylated tri- and pentamannosides, representing the structure of Davanat®, had an inhibitory effect of galectins comparable with that of free galactose. Further evaluation using cell-based assays, indirectly linked to galectin-3 inhibition, showed no inhibition of galectin-3 by the polysaccharides. These data suggest that the physiological effects of these plant polysaccharides are not due to inhibition of the canonical galectin carbohydrate-binding site.
一些复杂的植物源多糖，如改性柑橘果胶和半乳甘露聚糖，已被证明具有良好的抗炎和抗癌作用。大多数报告提出或声称这些作用是由于多糖与半乳糖凝集素相互作用，因为多糖含有可能结合这类凝集素的含半乳糖侧链。然而，它们与半乳糖凝集素进化保守的半乳糖苷结合位点的直接结合和/或抑制作用尚未得到证实。我们使用成熟的荧光各向异性测定法，测试了几种此类多糖与一系列生理浓度半乳糖凝集素的直接相互作用。所测试的生物活性果胶样品对所测试半乳糖凝集素的典型半乳糖苷结合位点的抑制作用非常弱，少数样品的IC50值>10 mg/ml，在大多数情况下根本没有抑制活性。半乳甘露聚糖Davanat®活性更高，尽管不是强抑制剂（IC50值根据半乳糖凝集素不同，在3至20 mg/ml范围内）。此外，还测试了在果胶和半乳甘露聚糖侧链和主链中发现的纯合成寡糖片段。果胶中最常见的半乳聚糖构型对所测试的半乳糖凝集素没有抑制作用。代表Davanat®结构的半乳糖基化三甘露糖苷和五甘露糖苷对半乳糖凝集素的抑制作用与游离半乳糖相当。使用与半乳糖凝集素-3抑制间接相关的基于细胞的测定法进行的进一步评估表明，这些多糖对半乳糖凝集素-3没有抑制作用。这些数据表明，这些植物多糖的生理作用并非由于抑制典型的半乳糖凝集素碳水化合物结合位点。
