The substrate specificity of the enzyme endo-alpha-N-acetyl-D-galactosaminidase from Diplococcus pneumonia
The substrate specificity of the enzyme endo-alpha-N-acetyl-D-galactosaminidase from Diplococcus pneumonia
复制标题
DOI：
10.1023/a:1018585604073
复制
发表时间：
1997-02-01
影响因子：
3
通讯作者：
Savage, AV
中科院分区：
文献类型：
--
作者：
Brooks, MM;Savage, AV
使用牛颌下粘蛋白和重塑的抗冻糖蛋白作为底物，重新检查了肺炎双球菌内切-α-N-乙酰-D-氨基半乳糖苷酶的底物特异性。与含有六种O-连接核心类型的去唾液酸牛颌下粘蛋白一起孵育表明，存在量非常少的二糖Gal β 1-3GalNAc是唯一释放的聚糖，而二糖GlcNAc β 1-3GalNAc是存在的主要结构，其他二糖没有释放。为了测试是否释放了唾液酸α 2-3连接到Gal或α 2-6连接到GalNAc的核心二糖Gal β 1-3GalNAc，将酶与含有（1）[H-3]NeuAc α 2-3Gal β 1-3GalNAc和（2）Gal β 1-3[[C-14]NeuAc α 2-6]GalNAc作为底物的重构抗冻糖蛋白一起孵育。未释放含NeuAc的三糖。这些结果有助于澄清许多研究人员对这种酶对一些新描述的核心类型和唾液酸化底物的活性的怀疑。
The substrate specificity of the enzyme endo-alpha-N-acetyl-D-galactosaminidase from Diplococcus pneumonia was re-examined using bovine submaxillary mucin and remodelled antifreeze glycoprotein as substrates. Incubation with desialylated bovine submaxillary mucin, which contains six O-linked core types, indicated that the disaccharide Gal beta 1-3GalNAc, which is present in very small amount, was the only glycan released, while the disaccharide GlcNAc beta 1-3GalNAc, which is the major structure present, and other disaccharides, were not released. To test whether the core disaccharide Gal beta 1-3GalNAc with sialic acid linked alpha 2-3 to the Gal or linked alpha 2-6 to the GalNAc was released, the enzyme was Incubated with remodelled antifreeze glycoprotein containing (1) [H-3]NeuAc alpha 2-3Gal beta 1-3GalNAc and (2) Gal beta 1-3[[C-14]NeuAc alpha 2-6]GalNAc as substrates. No NeuAc-containing trisaccharide was released. These results serve to clarify the doubts of many researchers regarding the activity of this enzyme on some newly-described core types and on sialylated substrates.