Glycogen storage disease Ib: modification of alpha 1-antitrypsin glycoprotein microheterogeneity.

Upon isoelectric focusing, alpha 1-antitrypsin shows a characteristic major band pattern caused by glycoprotein isoforms with different oligosaccharide side chains. In ten apparently healthy individuals with the Pi type MM the ratio of isoforms I, II, and III was 5.2:3.9:1.0. In six patients with glycogen storage disease Ib the ratio of isoforms in the Pi type MM was 3.6:5.5:1.9 suggesting a shift from the biantennary to triantennary oligosaccharide side chains. This shift may result from the limited availability of glucose or glucose derivatives for the synthesis of N-glycosidic glycoproteins.