Endo Y, Yamashita K, Han Y N, Iwanaga S, Kobata A
J Biochem. 1977 Aug;82(2):545-50.
Fragment 1, released from bovine plasma high-molecular-weight kininogen by the action of plasma kallikrein, is a glycopeptide with approximately 3 mol of each of N-acetylgalactosamine, galactose and sialic acid in one molecule. All these sugars were in the T-1 fragment obtained by tryptic digestion of fragment 1. Sialic acid can be completely released from the T-1 fragment by sialidase digestion. When this sialic acid-free T-1 fragment was incubated with purified diplococcal endo-alpha-N-acetylgalactosaminidase, all remaining sugars were released as a disaccharide. By Smith degradation and beta-galactosidase digestion, the structure of this disaccharide was found to be Gal beta 1 leads to 3GalNAc. Methylation analysis of the trisaccharide released from fragment T-1 by alkaline borohydride treatment indicated that all the galactose was obtained as the 2,4,6-tri-O-methyl derivative. Based on this evidence, the complete structure of the carbohydrate moieties of fragment 1 was proposed as Sialyl alpha 2 leads to 3Gal beta 1 leads to 3GalNAc. In addition, small amounts of a tetrasaccharide, Sialyl alpha 2 leads to 3Gal beta 1 leads to 3(Sialyl alpha 2 leads to 6)GalNAc also occurred as a carbohydrate chain of fragment 1.
片段1是一种糖肽，由血浆激肽释放酶作用于牛血浆高分子量激肽原释放而来，一个分子中大约含有3摩尔的N-乙酰半乳糖胺、半乳糖和唾液酸。所有这些糖类都存在于通过胰蛋白酶消化片段1得到的T-1片段中。唾液酸可通过唾液酸酶消化从T-1片段中完全释放出来。当将这种不含唾液酸的T-1片段与纯化的双球菌内切α-N-乙酰半乳糖胺酶一起孵育时，所有剩余的糖类都以二糖形式释放出来。通过史密斯降解和β-半乳糖苷酶消化，发现这种二糖的结构为Galβ1→3GalNAc。通过碱性硼氢化钠处理从片段T-1释放的三糖的甲基化分析表明，所有的半乳糖都以2,4,6-三-O-甲基衍生物的形式获得。基于这些证据，片段1碳水化合物部分的完整结构被推测为唾液酸α2→3Galβ1→3GalNAc。此外，少量的四糖，唾液酸α2→3Galβ1→3（唾液酸α2→6）GalNAc也作为片段1的碳水化合物链出现。
