The relationship of α-l-iduronidase and Hurler corrective factor

Hurler corrective factor (the protein that normalizes the faulty mucopolysaccharide catabolism of fibroblasts derived from Hurler patients) was previously identified as the enzyme α-l-iduronidase. However, not all α-l-iduronidase functions as Hurler corrective factor. The corrective and noncorrective forms of the human urinary enzyme have been separated from each other by chromatography on Sepharose-bound heparin. They have similar catalytic properties, some difference in ability to bind to the galactose-specific lectin of castor bean, and a significant difference in molecular weight (87,000 and 67,000 for the corrective and noncorrective forms, respectively). Only the corrective form is efficiently internalized by Hurler fibroblasts.