The release of carbohydrate moieties from human fibrinogen by almond glycopeptidase without alteration in fibrinogen clottability

Abstract

The possible noninvolvement of the carbohydrate moiety of human fibrinogen in the clotting mechanism was examined by eliminating the neutral sugar chains from desialylated fibrinogen by almond glycopeptidase digestion. 40% of the total neutral sugars was removed from the desialylated fibrinogen. The neutral sugars from both the β- and γ-polypeptide chains were released equally. The protein moiety of the glycopeptidase-digested fibrinogen was found to be intact. No significant change was observed in the thrombin time (fibrinogen clottability) of the resultant fibrinogen. The results suggest that the carbohydrate moiety of fibrinogen is not involved in the clotting mechanism. Oligosaccharide was detected in the glycopeptidase digest of desialylated fibrinogen by thin-layer chromatography (TLC), and was found to be identical with those released quantitatively from the peptic digests of β- and γ-polypeptide chains. The structure of the sugar chain was identified tentatively as Gal₂-GlcNAc₂-Man₃-GlcNAc₂, by sequential exoglycosidase digestion and quantitative analysis of carbohydrate components.