Mass spectrometry in the analysis of N-linked and O-linked glycans

Abstract

Mass spectrometry continues to play a vital role in defining the structures of N-and O-glycans in glycoproteins via glycomic and glycoproteomic methodologies. The former seeks to define the total N-and/or O-glycan repertoire in a biological sample whilst the latter is concerned with the analysis of glycopeptides. Recent technical developments have included improvements in tandem mass spectrometry (MS/MS and MS n ) sequencing methodologies, more sensitive methods for analysing sulfated and polysialylated glycans and better procedures for defining sites of O-glycosylation. New tools have been introduced to assist data handling and publicly accessible databases are being populated with glycomics data. Progress is exemplified by recent research in the fields of glycoimmunology, reproductive glycobiology, stem cells, bacterial glycosylation and non-mucin Oglycosylation.

Polylactosaminoglycan Glycomics: Enhancing the Detection of High-molecular-weight N-glycans in Matrix-assisted Laser Desorption Ionization Time-of-flight Profiles by Matched Filtering

“…Glycosylation is one of the most common and important post-translational modifications of proteins, yet it is also one of the most difficult to study because of its great complexity. Much of what we know about glycosylation, especially tissueand organism-specific variation, has been gathered via mass spectrometric profiling of detached glycans (1)(2)(3)(4). International, multi-laboratory comparisons of MS 1 and chromatographic glycomic data derived from standardized glycoproteins have concluded that the MS analysis of permethylated derivatives of released N-and O-linked glycans is the most robust glycomics strategy with respect to both sensitivity and quantitative reliability (5,6).…”

Metabolism of Vertebrate Amino Sugars with N-Glycolyl Groups

“…Indeed, some organisms exploit this substrate promiscuity by diversifying the repertoire of available substrates (9). These "errors," which arise from the loose substrate specificity of the enzyme, can give rise to further diversification of an already heterogeneous population of glycoforms (10). Such variations may offer evolutionary advantages (11) or, alternatively, remain as an evolutionary relic (12).…”

The Emerging Field of Diagnostics in Glycosylation Disorders

“…O-glycans cannot be removed from their sites enzymatically but have to be removed through alkaline b-elimination or hydrazinolysis, which in-turn denatures the peptide or proteins and thus does not allow any further site occupancy analyses to be undertaken. Technological advances in mass spectrometry are promising for improved N-and O-glycan analysis [26]. The ability of Quadrupole Time of Flight (QToF) instrumentation to facilitate MS experiments, especially on glycans which have been derivatised by permethylation, is allowing clear structural assignment of isomeric glycans [27].…”