Human
beta-trace protein is a major intrathecally synthesized
polypeptide constituent of human cerebrospinal fluid. We have previously shown that this
protein is almost quantitatively modified with biantennary complex-type N-linked
oligosaccharides which show "brain-type" glycosylation characteristics (Hoffmann,A. et al., J. Neurochem., 63, pp. 2185-2191, 1994). In the present study human
beta-trace protein from the cerebrospinal fluid (CSF) of patients with
carbohydrate-deficient glycoprotein syndrome (CDGS) due to
phosphomannomutase (PMM) deficiency and N-acetyl-glucosaminyltransferase
II (GlcNAc-T II) deficiency as well as from control individuals was studied by Western blot analysis. The
protein from pooled CSFs was purified by immunoaffinity chromatography. The
protein from the five patients with CDGS PMM deficiency showed three
protein bands upon SDS-PAGE analysis corresponding to the di-, mono-, and unglycosylated
polypeptide forms.
Carbohydrate structural analysis of the enzymatically liberated N-
glycans was performed applying mapping by HPAEC-PAD, methylation analysis as well as MALD/TOF-MS. Essentially identical
oligosaccharide structures were detected in beta-TP from type I patients and control adult pooled CSF. The
beta-trace protein from two patients with
GlcNAc-T II deficiency showed a single di-N-
glycosylated protein band with a significantly lower molecular weight than the di-glycosylated
polypeptide from control patients and the
beta-trace protein from pooled adult CSF. Beta-TP from
GlcNAc-T II deficiency patients shared only three
oligosaccharides out of the 13 observed in beta-TP from controls or patients with PMM deficiency. The major
oligosaccharide structures of the
glycoprotein from patients with
GlcNAc-T II deficiency were found to be monoantennary asialo- or monosialylated
lactosamine-type chains with proximal
fucose and bisecting GlcNAc.