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Does Matrix‐assisted Laser Desorption/Ionization Mass Spectrometry Allow Analysis of Carbohydrate Heterogeneity in Glycoproteins? A Study of Natural Human Interferon‐γ
Author(s) -
Mørtz Ejvind,
Sareneva Timo,
Julkunen Ilkka,
Roepstorff Peter
Publication year - 1996
Publication title -
journal of mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 1076-5174
DOI - 10.1002/(sici)1096-9888(199610)31:10<1109::aid-jms400>3.0.co;2-9
Subject(s) - chemistry , glycan , mass spectrometry , matrix assisted laser desorption/ionization , sialic acid , fragmentation (computing) , glycosylation , glycoprotein , mass , chromatography , mass spectrum , biochemistry , desorption , organic chemistry , adsorption , computer science , operating system
Interferon‐γ (IFN‐γ) is a dimeric, secretory glycoprotein produced by T‐lymphocytes. The glycan microheterogeneity of natural human IFN‐γ was characterized by matrix‐assisted laser desorption/ionization mass spectrometry (MALDI/MS) combined with glycosidase digestion. The glycan structures at the two potential glycosylation sites, asparagine 25 and 97, differ in composition and heterogeneity. The glycan at Asn 25 consists of a mixture of hybrid structures and fucosylated complex bi‐, tri‐ and tetra‐antennary structures, whereas the glycan at Asn 97 is more heterogeneous and consists of a mixture of high mannose structures, hybrid structures and unfucosylated complex bi‐ and tri‐antennary structures. The contribution to the observed glycan heterogeneity by prompt and metastable fragmentation was evaluated by treatments with different exoglycosidases and by comparison of linear, reflected and delayed extraction MALDI/TOF mass spectra. Heterogeneity observed with the matrices α‐cyano‐4‐hydroxycinnamic acid, 2,5‐dihydroxybenzoic acid and 2,4,6‐trihydroxyacetophenone was compared. Most of the heterogeneity can be attributed to native structure diversity and only to a minor extent to mass spectrometric fragmentation such as fragmentational loss of sialic acid residues.