Glycoforms of six serum glycoproteins in a patient with congenital disorder of glycosylation type I

In this paper the occurrence and relative content of defectively glycosylated serum glycoforms in transferrin (Tf), alpha1-acid glycoprotein (AGP), haptoglobin (Hp), alpha1-antitrypsin (alpha1-AT), alpha2-macroglobulin (alpha2-MG) and ceruloplasmin (Cpl) in the serum of a patient with congenital disorder of glycosylation type I are reported. Blood samples were taken when the patient was 14 years old and then after a one-year interval. The patterns of glycoforms in both samples were compared. In 4 out of 6 examined glycoproteins, glycoforms lacking one and two oligosaccharide chains occurred. "Underglycosylated" glycoforms of alpha2-MG and Cpl were not clearly detectable. Tf was shown to be affected with this defect to a higher extent than other glycoproteins, containing only 30% properly glycosylated molecules and also as much as 30% of the molecules lacking two glycan units. In Hp and alpha1-AT the proportions of properly and defectively glycosylated forms were similar. This properly glycosylated form comprised 47% of the Hp and 51-55% of the alpha1-AT molecules. As in AGP and Tf, about 30% the of molecules lacked one glycan unit. Twenty-one percent of the Hp molecules were devoid of two glycans, and this amount slightly increased in the course of the year. In alpha1-AT, 19 and 17% of the molecules lacked two glycans in both samples, respectively. Only in AGP we did find a substantial difference between the two blood samples. In the course of the year, the amount of the form lacking 2-chains decreased from 12 to 3%, resulting in a simultaneous increase in the forms lacking one chain and the properly glycosylated. Our work also indicates, that applying a simple method of biochemical analysis such as SDS-PAGE/Western-blotting could be helpful in preliminary diagnosis and could improve the identification of congenital disorders of glycosylation.