Recent progress in quantitative glycoproteomics.

Protein glycosylation is acknowledged as one of the major posttranslational modifications that elicit significant effects on protein folding, conformation, distribution, stability, and activity. The changes in glycoprotein abundance, glycosylation degree, and glycan structure are associated with a variety of diseases. Therefore, the quantitative study of glycoproteomics has become a new and popular research topic, and is quickly emerging as an important technique for biomarker discovery. Mass spectrometry-based protein quantification technologies provide a powerful tool for the systematic and quantitative assessment of the quantitative differences in the protein profiles of different samples. Combined with various glycoprotein/glycopeptide enrichment strategies and other glycoprotein analysis methods, these techniques have been further developed for application in quantitative glycoproteomics. A comprehensive quantitative analysis of the glycoproteome in a complex biological sample remains challenging because of the enormous complexity of biological samples, intrinsic characteristics of glycoproteins, and lack of universal quantitative technology. In this review, recently developed technologies in quantitative glycoproteome, especially those focused on two of the most common types of glycosylation (N-linked and O-linked glycoproteome), were summarized. The strengths and weaknesses of the various approaches were also discussed.