Determination of pancreatic carboxypeptidase A in human blood serum

A method has been designed for the assay of pancreatic carboxypeptidase A in blood serum. It uses Z-Gly-Phe as the substrate and fluorimetric determination of the released phenylalanine in an amino acid analyser, which yields a measure of free carboxypeptidase A. In addition, the sum (free carboxypeptidase A + procarboxypeptidase A) can be determined on a second portion preincubated with trypsin, which converts the proenzyme to the active form. Determinations made in fifteen healthy individuals showed the presence of a measurable concentration of free carboxypeptidase A. In acute pancreatitis, total carboxypeptidase A is raised. An increase in circulating proenzyme is observed in some cases. Data from 46 patients show a good correlation between total carboxypeptidase A, lipase and immunoreactive trypsin. Differential determination of procarboxypeptidase A and free carboxypeptidase A provides an interesting new tool for the diagnosis of pancreatic disorders.