Use of glycosidase digested human chorionic gonadotropin beta-subunit to explain the partial binding of ectopic...

Recent studies have demonstrated that ectopic glycoprotein hormones only partially bind Con A. To investigate the basis for these findings, the Con A binding of ectopic hCG beta from DoT cervical carcinoma cells was examined after digestion with various glycosidases. Ectopic hCG beta only partially bound Con A, as was the case after digestion with neuraminidase and beta-galactosidase. However, subsequent digestion with N-acetylhexosaminidase increased Con A binding to 96%. It is apparent that Con A binding of ectopic hCG can be inhibited by a residue removed by N-acetylhexosaminidase, probably extra beta-N-acetylglucosamine linked to beta-mannose on N-linked oligosaccharides. The method used involved the glycosidase digestion of glycoprotein alkylated under denaturing conditions and was first validated with milligram amounts of standard hCG beta.