Band 3 glycoprotein and glycophorin A from erythrocytes of children with congenital disorder of glycosylation type-la are underglycosylated

Band 3 and PAS-1 (a dimer of glycophorin A) from erythrocyte membranes of t hree children with congenital disorder of glycosylation, type Ia (CDG-Ia), aged 1 month, 3 years and 10 years respectively, were examined by a new tec hnique that allowed determination of carbohydrate molar composition of glyc oproteins separated by sodium dodecyl sulfate polyacrylamide gel electropho resis. In CDG children a single N-glycan of band 3 glycoprotein was hypogly cosylated and its mannose content was normal or elevated. Glycophorin A whi ch is the major carrier of erythrocyte sialic acid, was deficient in N-acet ylgalactosamine, and sialic acid residues. This finding indicated a partial unglycosylation of O-glycans in glycophorin A. In keeping with the results of PAS-1 analysis, total sialic acid in erythrocyte membranes from CDG chi ldren was reduced to 40-56 % of normal values. A possible molecular mechani sm of hypo- and unglycosylation of band 3 and glycophorin A, respectively, in CDG is discussed.