Schneider A B, Dudlak D
Department of Medicine, Michael Reese Hospital and Medical Center, University of Chicago, Illinois 60616.
Endocrinology. 1989 Jan;124(1):356-62. doi: 10.1210/endo-124-1-356.
Human thyroglobulin (TG) is one of a growing number of glycoproteins that are known to contain sulfate. Among these TG is unusual because it contains sulfate on both its asparagine-linked complex carbohydrate units and its single chondroitin 6-SO4 unit. We incubated tissue fragments prepared from normal and neoplastic thyroid tissue with [35S]sulfate to study the incorporation of sulfate into these two types of carbohydrate acceptor sites. Incubation conditions (0.1 mM sulfate for 16 h) were selected that maintained linear incorporation of [35S]sulfate and retention of more than 90% of iodinated TG in the tissue. Enzyme susceptibility was used to determine incorporation into the complex carbohydrate units (endoglycosidase-F) and the chondroitin 6-SO4 unit (chondroitin ABC lyase). In a representative experiment, 29.8% of the incorporated sulfate was found in the chondroitin 6-SO4 unit during the first hour of incubation. This increased progressively to 72.5% in the chondroitin unit during the incubation period from 8-16 h. A reciprocal decrease occurred in the proportion of sulfate incorporated into the complex carbohydrate units. TG released into the medium and retained in the tissue had the same ratio of sulfate in the two types of carbohydrate units. Neoplastic thyroid tissue incorporated more [35S]sulfate into TG than normal thyroid tissue from the same patient. Neoplastic and normal tissue differed further in the ratios of sulfate incorporated into the two types of carbohydrate units. We conclude that the incorporation of sulfate into the two types of sulfate-containing carbohydrate units of TG does not occur in a fixed ratio and that this differential incorporation of sulfate does not appear to be related to its release from the tissue.
人甲状腺球蛋白（TG）是已知含有硫酸盐的越来越多的糖蛋白之一。在这些糖蛋白中，TG不同寻常，因为它在其天冬酰胺连接的复合碳水化合物单元和单个硫酸软骨素6 - SO4单元上都含有硫酸盐。我们用[35S]硫酸盐孵育从正常和肿瘤性甲状腺组织制备的组织片段，以研究硫酸盐掺入这两种碳水化合物受体位点的情况。选择的孵育条件（0.1 mM硫酸盐，孵育16小时）可维持[35S]硫酸盐的线性掺入，并使组织中碘化TG的保留率超过90%。利用酶敏感性来确定硫酸盐掺入复合碳水化合物单元（内切糖苷酶 - F）和硫酸软骨素6 - SO4单元（软骨素ABC裂解酶）的情况。在一个代表性实验中，孵育的第一个小时内，29.8%掺入的硫酸盐存在于硫酸软骨素6 - SO4单元中。在8 - 16小时的孵育期内，该比例在硫酸软骨素单元中逐渐增加至72.5%。掺入复合碳水化合物单元的硫酸盐比例则相应下降。释放到培养基中并保留在组织中的TG在两种碳水化合物单元中的硫酸盐比例相同。来自同一患者的肿瘤性甲状腺组织比正常甲状腺组织将更多的[35S]硫酸盐掺入TG中。肿瘤组织和正常组织在掺入两种碳水化合物单元的硫酸盐比例方面也存在进一步差异。我们得出结论，硫酸盐掺入TG的两种含硫酸盐碳水化合物单元并非以固定比例发生，且这种硫酸盐的差异掺入似乎与其从组织中的释放无关。
