Figure 3.

Changes in N-Glycosylation with Galactose Therapy

(A) Transferrin isoforms were quantitated by HPLC from serum samples and expressed as percentage of total; during galactose supplementation, normalization of glycosylation is seen. Galactose was given on day 1–29, interrupted from day 30 to 43, and then reinstated. Note the steep decline in tetrasialo-transferrin in the short interval between the two therapy intervals. Tetrasialo-transferrin reached stable values within the normal range approximately 2 months after initiation of the second therapy interval.

(B) ESI-TOF mass spectra, before and after 120 days of therapy, identifies the partially defective N-glycans attached to serum transferrin. Whereas the mass spectrum before therapy identified mostly transferrin isoforms with defective galactosylation, 120 days of therapy resulted in a normal glycosylation profile with correct galactosylation. The different N-glycan species are indicated below; only one (of sometimes several) possible structures is depicted.