Lechner O, Dirnhofer S, Gerth R, Merz W E, Wick G, Berger P
Institut für Biomedizinische Alternsforschung, Osterreichische Akademie der Wissenschaften, Innsbruck.
Wien Klin Wochenschr. 1995;107(1):15-9.
The pregnancy and tumor marker human chorionic gonadotropin (hCG) belongs to the family of the glycoprotein hormones. Information on epitope forming sequences of hCG and its subunits hCG alpha and hcg beta has significant impact on the examination of intra- and extracellular metabolism and the standardization of diagnostic assay systems. Variants of hCG appear in biological fluids with variable modifications on different parts of the molecule. These changes may influence the binding patterns of monoclonal antibodies (MCA), thereby causing erroneous results in hCG immunoassays. The aim of the present work was to investigate the influence of peptide bond cleavages and the loss of certain segments of the molecule, which were induced by proteases on the expression of the seven hCG alpha-(alpha 1-alpha 7), nine hCG beta- (beta 1-beta 9) and four hCG beta-core-fragment-epitopes (beta 10-beta 13), previously identified by us [1-10]. To this end, we digested hCG alpha and hCG beta with chymotrypsin. Hormone fragments were separated by high performance liquid chromatography (HPLC) and subsequently immunochemically examined by direct binding radioimmunoassay (DB-RIA), competitive RIA and immunoenzymometric assays (IEMA). Fractions containing hCG-like immunoreactivity were sequenced by Edman and carboxypeptidase-Y degradation. It appeared that: (I) Amino acids (AA) alpha 41-47 and the peptide bonds between AA alpha 40/41, alpha 47/48 and alpha 29/30 do not influence the expression of the 7 alpha-epitopes, (II) The absence of the hCG beta N-terminus plays a crucial role for the formation of epitopes beta 10 and beta 13. (III) Neither the presence nor the absence of the C-terminal peptide of hCG beta (hCG beta CTP, AA beta 114-145) has any importance for the expression of epitopes beta 1-beta 7 and beta 10-beta 13 (IV).(ABSTRACT TRUNCATED AT 250 WORDS)
妊娠及肿瘤标志物人绒毛膜促性腺激素（hCG）属于糖蛋白激素家族。关于hCG及其亚基hCGα和hCGβ表位形成序列的信息，对细胞内和细胞外代谢的检测以及诊断检测系统的标准化具有重要影响。hCG变体出现在生物体液中，其分子不同部位有不同程度的修饰。这些变化可能影响单克隆抗体（MCA）的结合模式，从而在hCG免疫测定中导致错误结果。本研究的目的是调查蛋白酶诱导的肽键断裂和分子某些片段的缺失对先前我们鉴定出的7个hCGα表位（α1-α7）、9个hCGβ表位（β1-β9）和4个hCGβ核心片段表位（β10-β13）表达的影响。为此，我们用胰凝乳蛋白酶消化hCGα和hCGβ。激素片段通过高效液相色谱（HPLC）分离，随后通过直接结合放射免疫测定（DB-RIA）、竞争性RIA和免疫酶测定（IEMA）进行免疫化学检测。通过埃德曼降解法和羧肽酶-Y降解法对含有hCG样免疫反应性的组分进行测序。结果表明：（I）氨基酸（AA）α41-47以及AAα40/41、α47/48和α29/30之间的肽键不影响7个α表位的表达；（II）hCGβ N端缺失对表位β10和β13的形成起关键作用；（III）hCGβ C端肽（hCGβ CTP，AAβ114-145）的存在与否对表位β1-β7和β10-β13的表达均无影响；（IV）。（摘要截断于25０字）
