碳水化合物单元A或猪甲状腺球蛋白的结构。
Structure of carbohydrate unit A or porcine thyroglobulin.
作者信息
Tsuji T, Yamamoto K, Irimura T, Osawa T
出版信息
Biochem J. 1981 Jun 1;195(3):691-9. doi: 10.1042/bj1950691.
The unit A-type glycopeptides were purified from porcine thyroglobulin by Pronase digestion followed by chromatography on a DEAE-Sephadex A-25 column. These glycopeptides were separated into five fractions (UA-I, -II, -IV and -V) by Dowex 50W (X2) column chromatography. Fractions UA-I, -II, -III, -IV and -V were found to have the compositions (Man)9(GlcNAc)2-Asn, (Man)8(GlcNAc)2-Asn, (Man)7(GlcNAc)2-Asn, (Man)6(GlcNAc)2-Asn and (Man)5(GlcNAc)2-Asn respectively. The structures of these five fractions were investigated by the combination of exo- and endo-glycosidase digestions, methylation analysis. Smith periodate degradation and acetolysis. The results showed that fraction UA-V had the simplest structure: see formula in text. The larger glycopeptides (fractions UA-I, -II, -III and -IV) contained additional mannose residues alpha (1 leads to 2)-linked to the terminal mannose residues in the above core structure. These unit A-type glycopeptides appear to be biosynthetic intermediates that are to be processed to form complex-type glycopeptides (unit B-type sugar chains).
通过链霉蛋白酶消化，随后在DEAE-葡聚糖A-25柱上进行色谱分离，从猪甲状腺球蛋白中纯化出A-型单位糖肽。这些糖肽通过Dowex 50W（X2）柱色谱法分离成五个级分（UA-I、-II、-IV和-V）。发现级分UA-I、-II、-III、-IV和-V的组成分别为（甘露糖）9（N-乙酰葡糖胺）2-天冬酰胺、（甘露糖）8（N-乙酰葡糖胺）2-天冬酰胺、（甘露糖）7（N-乙酰葡糖胺）2-天冬酰胺、（甘露糖）6（N-乙酰葡糖胺）2-天冬酰胺和（甘露糖）5（N-乙酰葡糖胺）2-天冬酰胺。通过外切糖苷酶和内切糖苷酶消化、甲基化分析、高碘酸-史密斯降解和乙酰解相结合的方法研究了这五个级分的结构。结果表明，级分UA-V具有最简单的结构：见文中公式。较大的糖肽（级分UA-I、-II、-III和-IV）在上述核心结构的末端甘露糖残基上含有额外的以α（1→2）连接的甘露糖残基。这些A-型单位糖肽似乎是生物合成中间体，将被加工形成复合型糖肽（B-型单位糖链）。
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