Higginbotham J D, Heidelberger M, Gotschlich E C
Proc Natl Acad Sci U S A. 1970 Sep;67(1):138-42. doi: 10.1073/pnas.67.1.138.
Pyruvic acid is an immunological determinant of the quite rigorously type-specific capsular polysaccharide of pneumococcal type IV (S IV). Removal of pyruvic acid by mild hydrolysis converts the capsular polysaccharide of type IV into an analog of the pneumococcal group-specific C-substance. Depyruvylated S IV resembles C-substance so closely immunologically that it not only precipitates a high proportion of the anti-C in antipneumococcal sera, regardless of their immunological types, but also, like C, precipitates human C-reactive protein in the presence of calcium ions. Apparently, the removal of pyruvic acid ketal rings from adjacent sugars unmasks N-acetylgalactosamine residues which must be linked and spaced much as are those in C-substance. Groupings reactive with suitably linked N-acetylgalactosamine, therefore, appear to be located on the surfaces of molecules of human C-reactive protein.
丙酮酸是肺炎球菌4型（SIV）相当严格的型特异性荚膜多糖的免疫决定簇。通过温和水解去除丙酮酸可将4型荚膜多糖转化为肺炎球菌属特异性C物质的类似物。去丙酮酸化的SIV在免疫学上与C物质非常相似，以至于它不仅能沉淀抗肺炎球菌血清中高比例的抗C物质，而不论其免疫类型如何，而且还像C物质一样，在钙离子存在的情况下沉淀人C反应蛋白。显然，从相邻糖中去除丙酮酸缩酮环会暴露出N-乙酰半乳糖胺残基，这些残基的连接和间距必须与C物质中的残基大致相同。因此，与适当连接的N-乙酰半乳糖胺反应的基团似乎位于人C反应蛋白分子的表面。
