Specificity of β1,4-galactosyltransferase inhibition by 2-naphthyl 2-butanamido-2-deoxy-1-thio-β-D-glucopyranoside
作者:Yin Gao、Carmen Lazar、Walter A. Szarek、Inka Brockhausen
DOI:10.1007/s10719-010-9312-3
日期:2010.10
Inhibitors of Galactosyltransferase (GalT) have the potential of reducing the amounts of adhesive carbohydrates on secreted and cell surface-bound glycoproteins. We recently found a potent inhibitor of β4GalT, 2-naphthyl 2-butanamido-2-deoxy-1-thio-β-D-glucopyranoside (compound 612). In this work, we have tested compound 612 for the specificity of its inhibition and examined its effect on GalT, and on GlcNAc- and GalNAc-transferases in homogenates of different cell lines, as well as on recombinant glycosyltransferases. Compound 612 was found to be a specific inhibitor of β4GalT. The specificity of recombinant human β3GalT5 that also acts on GlcNAc-R substrates, revealed similarities to bovine milk β4GalT. However, 612 was a poor substrate and not an inhibitor for β3GalT5. To further determine the specific structures responsible for the inhibitory property of 612, we synthesized (2-naphthyl)-2-butanamido-2-deoxy-β-D-glucopyranosylamine (compound 629) containing nitrogen in the glycosidic linkage, and compared it to other naphthyl and quinolinyl derivatives of GlcNAc as substrates and inhibitors. Compound 629 was a substrate for both β4GalT and β3GalT5. This suggests that properties of 612 other than the presence of the naphthyl ring alone were responsible for its inhibitory action. The results suggest a usefulness of 612 in specifically blocking the synthesis of type 2 chains and thus epitopes attached to type 2 chains. In addition, 612 potently inhibits β4GalT in cell homogenates and thus allows assaying β3GalT activity in the presence of β4GalT.
半乳糖基转移酶(GalT)抑制剂有可能减少分泌的和细胞表面结合的糖蛋白上粘附的碳水化合物的数量。我们最近发现了一种有效的 β4GalT 抑制剂--2-萘基 2-丁酰胺基-2-脱氧-1-硫代-β-D-吡喃葡萄糖苷(化合物 612)。在这项工作中,我们测试了化合物 612 抑制作用的特异性,并研究了它对 GalT、不同细胞系匀浆中的 GlcNAc 和 GalNAc 转化酶以及重组糖基转移酶的影响。研究发现,化合物 612 是 β4GalT 的特异性抑制剂。重组人 β3GalT5 也作用于 GlcNAc-R 底物,其特异性与牛乳 β4GalT 相似。然而,612 是一种较差的底物,而不是 β3GalT5 的抑制剂。为了进一步确定 612 抑制性的具体结构,我们合成了糖苷键中含有氮的 (2-naphthyl)-2-butanamido-2-deoxy-β-D-glucopyranosylamine (化合物 629),并将其与 GlcNAc 的其他萘基和喹啉基衍生物作为底物和抑制剂进行了比较。化合物 629 既是β4GalT 的底物,也是β3GalT5 的底物。这表明,612 的抑制作用不仅仅是由于萘环的存在。结果表明,612 可特异性地阻断 2 型链的合成,从而阻断附着在 2 型链上的表位。此外,612 还能有效抑制细胞匀浆中的β4GalT,因此可以在存在 β4GalT 的情况下检测 β3GalT 的活性。