Glycoproteins are an important class of biological compounds. For example, gonadotropins, small glycoprotein hormones, regulate the activity of the pituitary. While these molecules are important biologically, they are very difficult to study. This is in part because of structural ambiguity of the carbohydrate on the protein. We take a novel approach to characterizing these compounds. First, the glycoprotein is subjected to enzymatic digestion, and glycopeptides are released. The resulting glycopeptides may be separated and are used in a variety of mass spectrometry studies. Several different types of mass spectrometric methods are utilized to identify substantial structural information about the glycopeptides. By performing these analyses on the glycopeptides, we may be able to learn information about glycoprotein structure that is not accessible using traditional approaches.
We are currently collaborating with Dr. George Bousfield at Wichita State University on a glycoprotein project involving the characterization of several human hormones. We have compared various mass spectrometric methods for the analysis of luteinizing hormone, (J. Am. Soc. Mass Spectrom. 2004, 15, 750-758), and recently, we have developed a new method, based on ion-pairing, to specifically identify sulfated glycopeptides in this hormone (J. Am. Soc. Mass Spectrom. In Press.) The methods we are developing could be applied as a general strategy for the characterization of any glycoprotein. In the specific case of the gonadotropins, this collaborative work may be helpful in improving the efficacy of hormone therapies.