Age-Dependent Variation in Glycosylation Features of Alpha-2-Macroglobulin

Alpha-2-macroglobulin (A2M) is a glycosylated broad spectrum inhibitor of numerous proteases, including those involved in blood coagulation. Glycosylation characteristics can affect protein structure and function. This study compares glycosylation characteristics of A2M in newborn umbilical cord (NUCP) and adult pooled plasmas. Peptide N-Glycosidase F treatment was used to evaluate the total N-glycan content of the molecules. Neuraminidase treatment, and affinity for Ricinus Communis Agglutinin I were used to examine terminal sialic acid and galactose content, respectively. Two-dimensional (2D) electrophoresis was used to determine charge-related isoform profiles and fluorophore-assisted carbohydrate electrophoresis (FACE) was used to characterize N-glycan profiles. Results revealed no difference in total N-glycan mass, however, a statistically significant difference was shown in the change in charge associated with sialic acid loss in the NUCP A2M population. 2D electrophoresis indicated a lower pI range for NUCP A2M isoforms. In addition, NUCP A2M displayed a trend toward higher terminal galactose quantities than adult A2M. FACE revealed an increased abundance of more branched, higher molecular weight glycans in NUCP A2M. These differences in glycan branching and charged residues may impact A2M receptor-based clearance and thus could be responsible for the increased A2M concentration seen in NUCP, and newborns.