An evaluation of serum "trypsin" tests.

When crystalline trypsin was dissolved at various concentrations in pooled serum, the rates of hydrolysis of z-benzoyl-1-arginineamide (BAA) and N-benzoyI-dlarginine-/ -naphthylamide (BANA) were not linear functions of the trypsin concentration. Also, the plot of trypsin activity in relation to trypsin concentration differed with different sera. The apparent tryptic activity toward these substrates is felt to be a function of the concentration of serum trypsin inhibitor and, with BANA oniy, some unidentifed proenzyme which is activated by trypsin. Therefore, it is concluded that it is not feasible to measure serum trypsin concentration with these substrates.