Fein H G, Rosen S W, Weintraub B D
J Clin Endocrinol Metab. 1980 Jun;50(6):1111-20. doi: 10.1210/jcem-50-6-1111.
The role of carbohydrate in the heterogeneity of hCG and its subunits is unclear. To study this question, we chromatographed over Sephadex G-100 an extract of term placenta as well as sera from a woman in the first and third trimesters of pregnancy and sera from two patients with nontrophoblastic malignancies. Samples were cochromatographed with radiolabeled urinary standards. hCG from first trimester pregnancy serum showed multiple peaks on G-100. The dominant peak eluted with an apparent molecular weight (72,000) higher than that of hCG from third trimester serum (63,000), urine (6),000), and placenta (59,000). hCG from both malignancy sera eluted with an apparent molecular weight (62,000) similar to that of hCG from third trimester and urinary hCG. Free hCG alpha from all sera eluted with a similar apparent molecular weight (29,000), which was higher than that of placental and urinary free alpha-subunit (22,000) and the alpha-subunit dissociated from intact hCG from all sources (22,000--23,000). The subunits were dissociated in the denaturing medium of 6 M guanidine-HCl, pH 3.0, and chromatographed in this medium over Sepharose CL-6B. This eliminated all of the differences in apparent molecular weight among corresponding forms that were found on G-100. All forms of hCG alpha coeluted with a chemically identified 80% deglycosylated hCG alpha. hCG and free alpha-subunits were incubated with mixed exoglycosidases which lacked detectable protease activity and were then rechromatographed on G-100. After deglycosylation, hCG from different sources eluted with a considerable heterogeneity (mol wt range, 40,000--50,000) not present in the native forms. Despite the heterogeneity of native free alpha-subunit from various sources, deglycosylation produced a common species with apparent molecular weights of 11,000--12,000, close to the chemically determined molecular weight of the polypeptide chain (10,400). These studies suggest that1) ectopic serum hCG and free alpha-subunit are similar to corresponding eutopic forms; 2) serum hCG and free alpha-subunit from all sources are more glycosylated than placental or urinary forms; 3) first trimester hCG is more glycosylated than other forms of hCG; and 4) serum free alpha-subunit is more glycosylated than the alpha-subunit which combines with hCG beta to form intact hCG.
碳水化合物在人绒毛膜促性腺激素（hCG）及其亚基异质性中的作用尚不清楚。为研究此问题，我们用葡聚糖凝胶G - 100对足月胎盘提取物、妊娠早期和晚期一名女性的血清以及两名非滋养层恶性肿瘤患者的血清进行了层析。样品与放射性标记的尿液标准品一起进行共层析。妊娠早期血清中的hCG在G - 100上显示出多个峰。主峰洗脱时的表观分子量（72,000）高于妊娠晚期血清（63,000）、尿液（6,000）和胎盘（59,000）中的hCG。两种恶性肿瘤血清中的hCG洗脱时的表观分子量（62,000）与妊娠晚期血清和尿液hCG的相似。所有血清中的游离hCGα洗脱时的表观分子量相似（29,000），高于胎盘和尿液中的游离α亚基（22,000）以及所有来源完整hCG解离出的α亚基（22,000 - 23,000）。亚基在6M盐酸胍（pH 3.0）的变性介质中解离，并在此介质中用琼脂糖CL - 6B进行层析。这消除了在G - 100上发现的相应形式之间表观分子量的所有差异。所有形式的hCGα与化学鉴定的80%去糖基化hCGα共洗脱。hCG和游离α亚基与缺乏可检测蛋白酶活性的混合外切糖苷酶一起孵育，然后在G - 100上重新层析。去糖基化后，不同来源的hCG洗脱时具有相当大的异质性（分子量范围为40,000 - 50,000），这在天然形式中不存在。尽管来自各种来源的天然游离α亚基存在异质性，但去糖基化产生了一种表观分子量为11,000 - 12,000的共同物种，接近多肽链的化学测定分子量（10,400）。这些研究表明：1）异位血清hCG和游离α亚基与相应的原位形式相似；2）所有来源的血清hCG和游离α亚基比胎盘或尿液形式的糖基化程度更高；3）妊娠早期hCG比其他形式的hCG糖基化程度更高；4）血清游离α亚基比与hCGβ结合形成完整hCG的α亚基糖基化程度更高。
