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. 