alpha-D-mannosidase in the liver and brain from patients with I-cell disease

The properties of alpha-D-mannosidase in the liver and brain from patients with I-cell disease were investigated, using 4-methylumbelliferyl-alpha-D-mannopyranoside as a substrate. A combination of chromatographies on DEAE-cellulose, concanavalin A-Sepharose and Sephacryl S-300 showed that intermediate alpha-D-mannosidase was present in the liver and brain from I-cell disease as well as control liver and brain, although an abnormal distribution of intermediate and acidic alpha-D-mannosidases occurred in the tissues from I-cell disease. These results suggested that a defect of intermediate alpha-D-mannosidase is unlikely to be the primary defect responsible for I-cell disease.