Dephosphorylation of intact glycoprotein to greatly improve digestion efficiency coupled with matrix-assisted laser desorption/ionization–Fourier transform ion cyclotron resonance mass spectrometric analysis

• Published in: Analytica chimica acta Vol. 787; pp. 140 - 147
• Main Authors: Li, Fenjie, Wang, Xiaodong, Liu, Yujie, Liu, Hui, Li, Zhili
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 17.07.2013
• Subjects: alkaline phosphatase; Animals; Cancer; Cattle; Cellular; Cyclotrons; Dephosphorylation; Digestion; Enrichment; fetuins; Fourier Analysis; Glycopeptides; Glycoprotein; glycoproteins; Glycoproteins - chemistry; Glycoproteins - metabolism; glycosylation; Humans; Intact glycoprotein; mass spectrometry; Mass Spectrometry - methods; Mathematical models; Matrix-assisted laser desorption/ionization–Fourier transform ion cyclotron resonance mass spectrometry; patients; peptidase K; phosphoric acid; phosphorylation; Phosphorylation - physiology; sialic acids; Sialylated glycopeptide; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization - methods; Strategy; thyroid neoplasms; Titanium dioxide; transferrin; CBB; IG/I(G-H2O); TPA; DTT; CDG; IAA; Dephosphorylation; Sialylated glycopeptide; ACN; TFA; SA; IG/I(G-SA); PTM(s); Intact glycoprotein; MALDI-FTICR MS; Matrix-assisted laser desorption/ionization–Fourier transform ion cyclotron resonance mass spectrometry; TP; ATP; Titanium dioxide; DHB; tryptic digestion followed by proteinase K digestion; tryptic digestion followed by proteinase K digestion and then alkaline phosphatase digestion; IG/I(G-HO); 2,5-dihydroxylbenzoic acid; post translational modification(s); carbohydrate-deficient glycoproteins; alkaline phosphatase digestion followed by tryptic digestion and then proteinase K digestion; acetonitrile; coomassie brilliant blue; dithiothreitol; trifluoroacetic acid; an intensity ratio of sialylated glycopeptide to its dehydrated counterpart, where G represents sialylated glycopeptide; sialic acid; an intensity ratio of sialylated glycopeptide to its less sialylated counterpart; iodoacetamide
• ISSN: 0003-2670; 1873-4324; 1873-4324
• DOI: 10.1016/j.aca.2013.05.044

•Dephosphorylation of intact glycoprotein to greatly improve digestion efficiency.•The enrichment efficiency for multisialylated glycopeptides were enhanced using phosphoric acid solution as elution buffer.•Validation was made by analyzing human serum α2-macroglobulin and transferrin. Sialylation is essential for a variety of cellular functions. Herein, we used bovine fetuin with three potential N-linked glycosylation sites containing complex-type glycan structures, four potential O-linked glycosylation sites and six potential phosphorylation sites as a model compound to develop a highly-efficient digestion strategy for sialylated glycoproteins and efficient enrichment strategy for sialylated glycopeptides using titanium dioxide. The former according to the process of alkaline phosphatase digestion followed by tryptic digestion and then proteinase K digestion could greatly improve the enzymatic efficiency on fetuin, and the latter could obviously enhance the enrichment efficiency for multisialylated glycopeptides using phosphoric acid solution as elution buffer. The mass spectra of the enriched glycopeptides derived from fetuin reveal that several series of the ion clusters with mass difference of 291Da correspond to the presence of multisialylated glycopeptides. In addition, the approach was applied to characterize the sialylated status of α2-macroglobulin and transferrin, respectively, from the sera of healthy subjects and sex- and age-matched patients with thyroid cancer, and their spectra indicate that the change in the amount of the glycoforms containing different number of sialic acid (SA) residues from one glycosylation site may be used to differentiate between healthy subjects and cancer cases.