Resistance to deglycosylation by ammonia of IgA1 O-glycopeptides: implications for the beta-elimination of O-glycans linked to serine and threonine.
Pools of O-glycopeptides (and their deglycosylated analogues) derived from trypsin-digested normal human serum IgA1 have been treated with ammonia under conditions reported to result in complete liberation of O-glycans linked to serine and threonine residues in glycopeptides and glycoproteins. MALDI-TOF MS analysis has revealed that only one of the six glycosylated sites is susceptible to beta-elimination under these conditions. It is likely that resistance to beta-elimination is due to very close proximity of proline to the glycosylated serine or threonine residues. Preliminary results using 0.1M NaOH (instead of ammonia) to perform beta-elimination indicated that there was also selective de-O-glycosylation with this reagent, however, these results were complicated by the concomitant hydrolysis of the peptide bonds. These findings may have implications for similarly O-glycosylated peptides and proteins and possibly for other chemical methods that are used to carry out beta-eliminations of O-glycans.
Tarelli
Edward
E
Medical Biomics Centre, St Georges University of London, Cranmer Terrace, London SW17 0RE, UK. tarelli@sgul.ac.uk
D000595:Amino Acid Sequence; D000641:Ammonia / Q000737:chemistry*; D000818:Animals; D002621:Chemistry / Q000379:methods*; D006020:Glycopeptides / Q000737:chemistry*; D006031:Glycosylation; D006801:Humans; D007070:Immunoglobulin A / Q000737:chemistry*; D008956:Models, Chemical; D008969:Molecular Sequence Data; D009439:Neuraminidase / Q000737:chemistry; D010455:Peptides / Q000737:chemistry; D012694:Serine / Q000737:chemistry; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013912:Threonine / Q000737:chemistry
D006020:Glycopeptides; D007070:Immunoglobulin A; D010455:Peptides; D013912:Threonine; D012694:Serine; D000641:Ammonia; D009439:Neuraminidase