Glycan Analysis of Prostate Specific Antigen (PSA) Directly from the Intact Glycoprotein by HR-ESI/TOF-MS

Glycans are important modulators of the biological function of proteins and are normally characterized from proteolytic glycopeptides or from (<i>N</i>-)­glycans released enzymatically by glycosidase treatment or chemically by hydrazinolysis. We demonstrate that glycan compositions can easily be determined directly by LC-ESI/TOF-MS from intact glycoproteins even with a very complex glycosylation pattern. Interpretation of isotopically resolved mass spectra of prostate specific antigen (PSA) using bioinformatics tools gives within a few hours the glycan compositions of 38 glycoforms.