Serafini-Cessi F, Dall'Olio F, Malagolini N
Carbohydr Res. 1986 Aug 15;151:65-76. doi: 10.1016/s0008-6215(00)90330-6.
This study reports the catalytic activity of N-acetyl-beta-D-galactosaminyltransferase from guinea-pig kidney towards such non-glycoprotein acceptors as small oligosaccharides and glycolipids, having a carbohydrate structure similar to that of the Sda antigen associated with human Tamm-Horsfall glycoprotein. 3'-O-Sialyllactose, but not 6'-O-sialyllactose or lactose, was an effective acceptor of the glycosyltransferase. On the basis of enzymic and chemical treatment of the tetrasaccharide obtained by the transfer of [14C]GalNAc to 3'-O-sialyllactose, we propose that the glycosyltransferase attaches beta-D-GalNAc to O-4 of the galactose residue that is substituted at O-3 by sialic acid. The GM3 ganglioside, in which the identical carbohydrate moiety of 3'-O-sialyllactose is bound to a ceramide residue, did not serve as an acceptor of the kidney-N-acetyl-beta-D-galactosaminyltransferase and did not behave as a competitive inhibitor of the Tamm-Horsfall glycoprotein in the transferase assay. These results indicate that the hydrophobic moiety in the ganglioside hinders the action of N-acetylgalactosaminyltransferase. Study of the transferase activity towards a heterogeneous glycopeptide species prepared from a Sd(a-) Tamm-Horsfall glycoprotein indicated that guinea-pig kidney enzyme preferentially transferred [14C]GalNAc to the oligosaccharides having a tetraantennary branching-structure.
本研究报道了豚鼠肾脏中的N-乙酰-β-D-半乳糖胺基转移酶对小寡糖和糖脂等非糖蛋白受体的催化活性，这些受体具有与 humans二糖相关的Sda抗原相似的碳水化合物结构。-Tamm-Horsfall糖蛋白。3'-O-唾液酸乳糖是糖基转移酶的有效受体，而6'-O-唾液酸乳糖或乳糖则不是。基于对通过将[14C]GalNAc转移到3'-O-唾液酸乳糖而获得的四糖进行酶促和化学处理，我们提出糖基转移酶将β-D-GalNAc连接到半乳糖残基的O-4位，该半乳糖残基在O-3位被唾液酸取代。GM3神经节苷脂中，3'-O-唾液酸乳糖的相同碳水化合物部分与神经酰胺残基结合，它不是肾脏N-乙酰-β-D-半乳糖胺基转移酶的受体，在转移酶测定中也不表现为Tamm-Horsfall糖蛋白的竞争性抑制剂。这些结果表明神经节苷脂中的疏水部分阻碍了N-乙酰半乳糖胺基转移酶的作用。对由Sd(a-)Tamm-Horsfall糖蛋白制备的异质糖肽种类的转移酶活性研究表明，豚鼠肾脏酶优先将[14C]GalNAc转移到具有四天线分支结构的寡糖上。
