The glycoprotein-degrading potential of peripheral leukocytes in cystic fibrosis

In this study, the potential problems and discrepancies in cill culture techniques were avoided by isolating leukocytes from the peripheral blood of patients with cystic fibrosis and healthy human volunteers and preparing homogenates to determine the specific activities of 5 lysosomal enzymes involved in the degradation of glycoproteins. Four lysosomal hydrolases involved in the breakdown of the carbohydrate side chain were assayed using artificial substrates. The fifth enzyme, aspartylglucosamine amido hydrolase, which cleaves the linkage between this side chain and the peptide backbone, was assayed with natural substrate. No differences in enzyme activities between the 2 leukocyte sources were observed. Because no enzyme activities were deficient and no compensatory increases were noted, we concluded that the thick, glycoprotein-rich, exocrine secretions in cystic fibrosis cannot be attributed to a defect in their catabolism.