Mass Spectrometry and Two-Dimensional Electrophoresis To Characterize the Glycosylation of Hen Egg White Ovomacroglobulin

Glycosylation of proteins plays an
important role in their biological
functions, such as allergenicity. Ovomacroglobulin (OVMG) is a glycoprotein
from hen egg white, but few studies have been done so far to delineate
the glycosylated sites of OVMG. The present study characterized the
glycosylation of OVMG using mass spectrometry and two-dimensional
electrophoresis. MALDI-TOF-MS showed that the OVMG subunit [M + H]+ ion has a peak at m/z 183297;
therefore, the carbohydrate moiety is calculated as 11.5% of the whole
OVMG molecule. HPLC-ESI-MS/MS confirmed that of 13 potential N-glycosylation
sites of OVMG, 11 sites were glycosylated; 1 site (N1221) was found in both glycosylated and nonglycosylated forms. On the
two-dimensional electrophoresis gel, a series of OVMG spots horizontally
distributed at 170 kDa, with an isoelectric point range of 5.03–6.03,
indicating the heterogeneity of glycosylation of OVMG. These results
provided important information for understanding of structure, function,
and potential allergenic sites of OVMG.