Deficiency of serum carboxypeptidase B-like (anaphylatoxin inactivator, carboxypeptidase N) activity in sera from patients with cystic fibrosis.

Serum from 95 patients with cystic fibrosis and 47 control subjects without 
cystic fibrosis was analyzed for carboxypeptidase B-like activity in the presence 
of optimal concentrations of Co2+ ion, hippuryl-L-lysine and serum. Fourteen of 
the cystic fibrosis patients had no steatorrhea and therefore minimal pancreatic 
dysfunction. Patients with cystic fibrosis and controls were of comparable age. 
Serum carboxypeptidase B-like activity was significantly decreased in cystic fibrosis patients 
including cystic fibrosis patients without steatorrhea. Significantly low values were found 
in both male and female cystic fibrosis patients when compared with 
controls of similar sex. Although values were unaffected by age in 
the control population, values in older patients with cystic fibrosis were 
significantly lower than values in younger patients. No correlation was obtained 
between serum carboxypeptidase B-like activity and pulmonary or hepatic function. Serum 
carboxypeptidase B-like activity therefore falls with progression of the disease and 
may limit the ability to degrade circulating peptides in older patients 
with cystic fibrosis. Deficient serum carboxypeptidase B-like activity is less likely, 
however, to be a factor in the development of the early 
manifestations of the disease. 