Protein and Site Specificity of Fucosylation in Liver-Secreted Glycoproteins

作者：Pompach Petr; Ashline David J; Brnakova Zuzana; Benicky Julius; Sanda Miloslav; Goldman Radoslav^*

来源：Journal of Proteome Research, 2014, 13(12): 5561-5569.

DOI：10.1021/pr5005482

• mass spectrometry
• exoglycosidase treatment
• microheterogeneity
• N-glycans
• permethylation
• MSn structural analysis glycopeptides
• hepatocellular carcinoma
• fucosylation
• site specificity

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.

• 出版日期2014-12