Human pancreatic chymotrypsinogen A: a non-competitive enzyme immunoassay, and molecular forms in serum and amniotic fluid

Abstract

A sandwich enzyme immunoassay has been developed for human pancreatic chymtrypsin(ogen) using polystyrene balls coated with specific IgG as the first antibody and peroxidase-labelled IgG as the second antibody. The detection limit was 0.5 μg/l. A good parallelism was observed with the curves obtained from standard chymotrypsinogen A and chymotrypsin(ogem) present in pancreatic juice: however, a slight discrepancy in parallelism with chymotrypsin(ogen) present in serum and amniotic fluid was noticed. Chymotrypsinogen concentration in pancreatic juice was evaluated to represent 9% of total proteins. Mean values of chymotrypsin(ogen) in human sera were 24.6±8.3 μg/l in adults and 20.9±8.8 μg/l in newborns. In amniotic fluid at the 18th week of pregnancy the values were scattered (5–70 μg/l). The molecular forms of immunoreactive chymotrypsin(ogen) in normal serum and amniotic fluid have been investigated by gel flitration of Sephadex G-100. Two peaks of immunoreactive chymotrypsin(ogen) were observed normal serum; the first peak elutes in a position consistent with a complex of chymotrypsin with serum ihibitor ( M r 76 000), and the second peak elutes with a molecular weight of approx. 25 000 corresponding to the elution position of free chymotyrpsin(ogen). In normal amniotic fluid three peaks of immunoreactive material were present; the first and second peaks elute same position as in serum, and the third peak with a molecular weight of about 14 500 may represent a degraded form of chymotrypsin.