Autoactivation of cationic trypsinogen variants in the presence of chymotrypsin C (CTRC). Trypsinogen was incubated at 1 μM concentration with 5 nM CTRC and 10 nM initial trypsin in 0.1 M Tris-HCl (pH 8.0), 1 mM CaCl2 and 0.05% Tween-20 (final concentrations) at 37° C. At the indicated times, 2 μL aliquots were removed and trypsin activity was measured as described in Experimental Procedures. Trypsin activity was expressed as percent of the maximal wild-type activity in the absence of CTRC. A, mutant with increased autoactivation, B, mutants with unchanged autoactivation; C, mutants with decreased autoactivation.