Use of a new synthetic substrate, Nalpha-tosyl-L-arginine-P-nitroanilide (TAPA), for determining trypsin activity in the duodenal contents.

The newly synthesized chromogenic substrate Nalpha-tosyl-L-arginine-p-nitroanilide (TAPA) was used to determine the trypsin activity (as the concentration and output in 20-min samples) of the duodenal contents before and after hormonal stimulation with cholecystokinin-pancreozymin (CPZ) and secretin (S). The results were compared with those obtained by means of Nalpha-benzoyl-D,L-arginine-p-nitroanilide (BAPA) and the Nalpha-tosyl-L-arginine methylester (TAME). The synthetic substrates were compared in 17 subjects with normal and in 8 subjects with pathological CPZ-S test values. A high degree of correlation was found in every case between the values obtained by means of the given substrates and it actually proved possible to determine the conversion coefficients for the trypsin concentration (BAPA = 1.306 TAPA, TAME = 0.509 TAPA) and for trypsin output (BAPA = 1.306 TAPA, TAME = 0.535 TAPA). The results demonstrate the usefulness of our new chromogenic substrate TAPA, which is more readily available and cheaper than BAPA and TAME for determining trypsin activity in biological material.