Radioimmunoassay of active pancreatic enzymes in sera from patients with acute pancreatitis. I. Active carboxypeptidase B.

Previous studies have suggested that measurement of active enzymes in relation to proenzymes in serum of patients with pancreatitis may reflect the degree of zymogen activation in the gland. Here we describe the first single-tube assay for an active form of a pancreatic enzyme that is ordinarily synthesized as a proenzyme. Human procarboxypeptidase B, which we purified to near homogeneity, is approximately 13 000 Da larger than the active enzyme (EC 3.4.17.2). Antibodies specific for active carboxypeptidase B were obtained by affinity chromatography of anti-carboxypeptidase B antisera on a gel containing procarboxypeptidase B, then used to develop a single-tube radioimmunoassay for measuring active carboxypeptidase B in serum. Using this assay, we were able to detect, for the first time, active carboxypeptidase B in sera from patients with acute pancreatitis. Preliminary data show a correlation between the serum concentrations of active carboxypeptidase B and those of active trypsin complexed with serum inhibitors, but no correlation with serum amylase values.