Molecular cloning, production and properties of recombinant FSH (Puregon~(R))

摘要

Follicle Stimulating Hormone (FSH), Luteinizing Hormone (LH) and Thyroid Stimulating Hormone from the pituitary, and human chorionic gonadotrophin (hCG) from the placenta belong to the family of glycoprotein hormones. These hormones have a heterodimeric structure, and contain two non-covalently linked α - and β subunits. The amino acid sequence of the α -subunits is identical, whereas the β -subunits differ and confers biological specificity on the individual gonadotrophins (Ulloa-Aquirre, 1988,1995). Only the intact dimer is biologically active; free subunits are inactive. Both the α - and β -subunits are glycosylated and contain N-linked carbohydrate chains. HCG contains four additional O-linked carbohydrates on the C-terminal peptide. Thestructure and sequence of the N-linked carbohydrates on the gonadotrophins may vary considerably. In particular the branching structure and the terminal residues on the oligosaccharides differ. The oligosaccharides in FSH terminate with sialic acid, whereas LH carbohydrates are sulphated. As a consequence of the microheterogeneity of the carbohydrate side chains, gonadotrophins consist of a mixture of molecules (isohormones) that differ in charge. Glycosylation is very important for the biological activity of gonadotrophins. It has been shown that the extent of terminal sialylation and or sulphation is the major determinant of the overall charge of the molecule and determines the in vivo clearance rate (De Leeuw et al, 1996). Thus, isohormones that contain less sialic acid are rapidly cleared, whereas the more acidic glycoforms have a long half-life.