Effect of activation peptide mutations on activation of human cationic trypsinogen with enteropeptidase. Approximately 100 nM wild-type or mutant trypsinogen (final concentration) was activated with 100 ng/ml bovine enteropeptidase (final concentration) as described in Materials and Methods. The activation reaction was followed by continuous monitoring of p-nitroanilide release at 405 nm as a measure of trypsin activity