Title : Protein and site specificity of fucosylation in liver-secreted glycoproteins
Abstract :
Chronic liver diseases are a serious health problem worldwide
One of the frequently reported glycan alterations in liver disease is aberrant fucosylation , which was suggested as a marker for noninvasive serologic monitoring
We present a case study that compares site specific glycoforms of four proteins including haptoglobin, complement factor H , kininogen-1 , and hemopexin isolated from the same patient
Our exoglycosidase-assisted LC-MS/MS analysis confirms the high degree of fucosylation of some of the proteins but shows that microheterogeneity is protein- and site-specific
MSn analysis of permethylated detached glycans confirms the presence of LeY glycoforms on haptoglobin , which cannot be detected in hemopexin or complement factor H ; all three proteins carry Lewis and H epitopes
Core fucosylation is detectable in only trace amounts in haptoglobin but with confidence on hemopexin and complement factor H , where core fucosylation of the bi-antennary glycans on select glycopeptides reaches 15-20% intensity
These protein-specific differences in fucosylation , observed in proteins isolated from the same patient source, suggest that factors other than up-regulation of enzymatic activity regulate the microheterogeneity of glycoforms
This has implications for selection of candidate proteins for disease monitoring and suggests that site-specific glycoforms have structural determinants , which could lead to functional consequences for specific subsets of proteins or their domains