Yamamoto Satoshi, Muramatsu Hisako, Muramatsu Takashi
Department of Biochemistry, Nagoya University Graduate School of Medicine, Showa-ku, Aichi, Japan.
Glycoconj J. 2005 Feb;22(1-2):35-42. doi: 10.1007/s10719-005-0847-7.
Endo-beta-N-acetylglucosaminidase D (Endo D) produced by Streptococcus pneumoniae hydrolyzes the di-N-acetylchitobiose structure in the core of complex-type asparagine-linked oligosaccharides, and has a molecular weight of 180 kDa. A truncated Endo D of 102 kDa in which 134 N-terminal amino acids and 599 C-terminal amino acids were deleted, still retained the enzymatic activity. The truncated Endo D has specificity indistinguishable from the intact enzyme, and also acted on the core structure of asparagine-linked oligosaccharides attached to intact IgG. Because of its lower molecular weight, the truncated enzyme may be useful as a tool for protein deglycosylation. The entire region of the truncated Endo D had 32% sequence identity to endo- beta-N-acetylglucosaminidase BH (Endo BH) from Bacillus halodurans, which acted on high-mannose type oligosaccharides. Chimeric constructs of the truncated Endo D and Endo BH showed no activity. Glutamic acid 324 (E 324) in Endo D is conserved in Endo BH and Endo M, and is an essential amino acid in Endo M. Mutation of E324 abolished Endo D activity. The specificity of Endo D for complex type oligosaccharides is probably defined by multiple domains in the Endo D structure.
肺炎链球菌产生的内切-β-N-乙酰氨基葡萄糖苷酶D（Endo D）可水解复杂型天冬酰胺连接寡糖核心中的二-N-乙酰壳二糖结构，其分子量为180 kDa。一种截短的Endo D，缺失了134个N端氨基酸和599个C端氨基酸，分子量为102 kDa，但仍保留酶活性。截短的Endo D与完整酶具有无法区分的特异性，并且也作用于与完整IgG相连的天冬酰胺连接寡糖的核心结构。由于其分子量较低，截短的酶可能作为蛋白质去糖基化的工具。截短的Endo D的整个区域与嗜碱芽孢杆菌的内切-β-N-乙酰氨基葡萄糖苷酶BH（Endo BH）有32%的序列同一性，Endo BH作用于高甘露糖型寡糖。截短的Endo D和Endo BH的嵌合构建体无活性。Endo D中的谷氨酸324（E324）在Endo BH和Endo M中保守，并且是Endo M中的必需氨基酸。E324的突变消除了Endo D的活性。Endo D对复杂型寡糖的特异性可能由Endo D结构中的多个结构域决定。
