THE IDENTIFICATION OF ABNORMAL GLYCOFORMS OF SERUM TRANSFERRIN IN CARBOHYDRATE-DEFICIENT GLYCOPROTEIN SYNDROME TYPE-I BY CAPILLARY ZONE ELECTROPHORESIS
O. Iourin et al., THE IDENTIFICATION OF ABNORMAL GLYCOFORMS OF SERUM TRANSFERRIN IN CARBOHYDRATE-DEFICIENT GLYCOPROTEIN SYNDROME TYPE-I BY CAPILLARY ZONE ELECTROPHORESIS, Glycoconjugate journal, 13(6), 1996, pp. 1031-1042
One of the biochemical characteristics of carbohydrate deficient glyco
protein syndromes is the presence of abnormal glycoforms in serum tran
sferrin. Both glycoform heterogeneity and variable site occupancy may,
in principle, lead to the generation of a range of glycoforms which c
ontain different numbers of sialic acid residues, and therefore variab
le amounts of negative charge. Capillary zone electrophoresis was used
to resolve the glycoforms of normal human serum transferrin and also
of a set of glycoforms which were prepared by digesting the sugars on
the intact glycoprotein with sialidase. The sugars on the intact glyco
protein were also modified by a series of exoglycosidase enzymes to pr
oduce a series of neutral glycoforms which were also analysed by capil
lary zone electrophoresis. The oligosaccharide population of human ser
um transferrin was analysed by a series of mixed exoglycosidase digest
s on the released glycan pool and quantified using a novel HPLC strate
gy. Transferrin was isolated from carbohydrate deficient glycoprotein
syndromes type I serum and both the intact glycoforms and released sug
ars were resolved and quantified. The data presented here confirm the
presence of a hexa-, penta- and tetra-sialoforms of human serum transf
errin in both normal and carbohydrate deficient glycoprotein syndrome
type I serum samples. Consistent with previous reports carbohydrate de
ficient glycoprotein syndrome type I transferrin also contained a di-s
ialoform, representing a glycoform in which one of the two N-glycosyla
tion sites is unoccupied, and a non-glycosylated form where both remai
n unoccupied. This study demonstrates that capillary zone electrophore
sis can be used to reserve quantitatively both sialylated and neutral
complex type glycoforms, suggesting a rapid diagnostic test for the ca
rbohydrate deficient glycoprotein syndromes group of diseases.