Yang B Y, Gray J S, Montgomery R
Department of Biochemistry, College of Medicine, University of Iowa, Iowa City 52242, USA.
Carbohydr Res. 1996 Jun 21;287(2):203-12. doi: 10.1016/0008-6215(96)00073-0.
Horseradish peroxidase (E.C. 1.11.1.7) isozyme c (HRPc) is a glycoprotein found to contain 21.8% carbohydrate with the average composition: 2 mol GlcNAc, 2.6 mol Man, and 0.8 mol each of Fuc and Xyl. The oligosaccharides of HRPc were investigated by a combination of High pH Anion-Exchange Chromatography with Pulsed Amperometric Detection, methylation analysis and Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry. The structure of the major oligosaccharide released by digestion with glycopeptidase A, accounting for between 75 and 80% of the total, was confirmed to be [sequence: see text]. Most of the remaining oligosaccharides were found to belong to the (Xyl)xManm(Fuc)fGlcNAc2 (m = 2, 4, 5, 6; f = 0 or 1; x = 0 or 1) family. Less than 5% of the oligosaccharides were of the ManmGlcNAc2 (m = 4 to 7) type. Methylation analysis of holo- and apo-HRPc and its tryptic glycopeptides support the structures proposed for the oligosaccharides. Furthermore, methylation analysis of the tryptic glycopeptides provides evidence for the heterogeneity of the oligosaccharides occurring at each of the N-linked sites.
辣根过氧化物酶（E.C. 1.11.1.7）同工酶c（HRPc）是一种糖蛋白，发现其含有21.8%的碳水化合物，平均组成为：2摩尔的N-乙酰葡糖胺、2.6摩尔的甘露糖，以及各0.8摩尔的岩藻糖和木糖。采用高pH值阴离子交换色谱与脉冲安培检测相结合、甲基化分析以及基质辅助激光解吸/电离飞行时间质谱法对HRPc的寡糖进行了研究。经肽-N4-(N-乙酰-β-葡糖胺)天冬酰胺酶A消化释放的主要寡糖结构（占总量的75%至80%）经确认是[序列：见原文]。发现其余大多数寡糖属于(Xyl)xManm(Fuc)fGlcNAc2（m = 2、4、5、6；f = 0或1；x = 0或1）家族。少于5%的寡糖属于ManmGlcNAc2（m = 4至7）类型。全酶和脱辅基HRPc及其胰蛋白酶糖肽的甲基化分析支持所提出的寡糖结构。此外，胰蛋白酶糖肽的甲基化分析为每个N-连接位点处寡糖的异质性提供了证据。
