Haptoglobin glycoforms in a case of carbohydrate-deficient glycoprotein syndrome

Alterations in haptoglobin (Hp) glycosylation were examined in the plasma of the first patient with carbohydrate-deficient glycoprotein syndrome (CDGS) who was described in Poland. Hp concentration in the CDGS patient plasma was low (240 mg/l) and the Hp phenotype was shown to be 2-2. Three glycoforms of the Hp beta subunit were observed in SDS-PAGE in CDGS. The densitometric analysis and molecular weight determinations suggested that 50% of glycoforms were fully glycosylated; 30% contained three out of four and 20% only two out of four glycan units compared to those that are present in Hp derived from healthy people. Results with lectins (concanavalin A and Sambucus nigra, Maackia amurensis and Alleuria aurantia agglutinins) indicate that all three glycoforms of beta subunit of CDGS-Hp contained biantennary complex glycans terminated with alpha 2,6 bound sialic acid, but without fucose or alpha 2,3 linked sialic acid. Hp glycosylation abnormalities described in this work suggest that this case was a type I carbohydrate-deficient glycoprotein syndrome.