Glycoproteins oligosaccharide release from

J. Charlwood, J. M. Skehel, and P. Camilleri, Analysis of /V-linkcd oligosaccharides released from glycoproteins separated by two-dimensional gel electrophoresis, Anal. Biochem., 284 (2000) 49-59. 

A variety of high-mannose oligosaccharides released from glycoproteins by enaymic cleavage have been separated chromatographically, derivatised either by reduction and... 

Complex carbohydrates released from glycoproteins were readily profiled by capillary gel electrophoresis with LIF-based detection of 1-aminopyrene-3,6,8-trisulfonic acid (APTS)-labeled sugar molecules (Figure 10) [125]. High-mannose-type oligosaccharides of ribonuclease B were derivatized by APTS and separated by capillary electrophoresis using polyethylene oxide separation medium [126]. 

Using MUNeuSAc as donor, the enzymatic sialylation of N-linked oligosaccharides released from the glycoproteins and derivatized with 2-aminopyridine has been reported, but no details on yields were provided.167... 

Removal of the oligosaccharide chain from the glycoprotein usually involves the use of one of three main methods treatment with NaOH-NaBH4, hydrazinolysis, or proteolysis.34-36 The NaOH-NaBH4 treatment is used to release, somewhat specifically, oligosaccharides O-linked to serine and threonine. Hydrazinolysis is used to break N-linkages, and proteolysis, to isolate glycopeptides. Each method apparently still has some drawbacks. 

Results of an experiment with an oligosaccharide free from amino acid were less conclusive, but were not incompatible with the structure shown. The oligosaccharide was prepared from a separated glycoprotein fraction having a D-mannose hexosamine ratio of 5 3. a-D-Mannosidase and 2-acetamido-2-deoxy-/3-D-glucosidase were used alternately. Initially, a-D-mannosidase removed about 1.5 D-mannose residues per molecule. Subsequent treatment of the residual oligosaccharide with 2-acetamido-2-deoxy-/3-D-glucosidase released rather less than one proportion of hexosamine residue, and then another 1.5 residues of D-mannose became open to attack by a-D-mannosidase. 

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