Mass spectrometric “sequencing” of oligosaccharides. Carbohydrate-cleaving enzymes were used to release and specifically cleave the oligosaccharide component of the glycoprotein fetuin from bovine serum. Parts A and B show the masses obtained with MALDI-TOF spectrometry as well as the corresponding structures of the oligosaccharide-digestion products: (A) digestion with peptide N-glycosidase F (to release the oligosaccharide from the protein) and neuraminidase; (B) digestion with peptide N-glycosidase F, neuraminidase, and β-1,4-galactosidase. Knowledge of the enzyme specificities and the masses of the products permits the characterization of the oligosaccharide. See Figure 11.16 for the carbohydrate key. [Data from A. Varki, R. D. Cummings, J. D. Esko, H. H. Freeze, G. W. Hart, and J. Marth (Eds.), Essentials of Glycobiology

(Cold Spring Harbor Laboratory Press, 1999), p. 596.]