ABSTRACT
Classically, the family of glycoprotein honnones includes luteinizing honnone (LH; lutropin), follicle-stimulating honnone (FSH; follitropin), and thyroid-stimulating honnone (TSH; thyrotropin) produced by the anterior pituitary as well as the chorionic gonadotropins (CG; choriogonadotropin) produced by the placenta. These four honnones have rather complex chemical structures because (1) they are heterodimers, (2) they contain numerous intrachain disulfide bonds, and (3) they are glycoproteins. The significance of glycoprotein hormone subunits as well as the structure of the peptide chains will be considered in detail in other chapters of this book (see Chapters I and 3). The structures of the oligosaccharides associated with these four glycoprotein honnones will be considered herein. Additional infonnation may be found in previous reviews which discuss this topic. 1-8
Beginning in the late 1950s significant progress was made in the purification and structural analysis of the glycoprotein honnones (reviewed by Liu and Ward;1 Parsons and Pierce3). However, only in the last decade has significant progress been made in elucidating the fine structure of their carbohydrate moieties. The oligosaccharides of certain glycoprotein hormones (e.g., human CG) have been described in detail. Infonnation is extremely limited in other cases, particularly with regard to FSH. When considering a given glycoprotein honnone (e. g., LH), variations in oligosaccharide structure occur between species. Moreover, any given glycoprotein honnone may possess oligosaccharides which vary slightly to markedly in their structures, even at a single glycosylation site. The observation that the common alpha subunit, assumed to be the product of a single gene, appears to possess distinct oligosaccharide structures when associated with different beta subunits9• lo is quite intriguing. Even more fascinating is the possibility that a single cell type, the gonadotrope, may produce two glycoprotein honnones with distinctly different oligosaccharide structures. 9•10 Assuming that the carbohydrate moieties are involved in the biological functions of honnones, it is desirable to have more complete infortnation regarding their oligosaccharide structures, particularly as glycoprotein honnones produced by recombinant DNA technology (e.g_, 11.12) become available.
