Figure 6.

Effect of calcium on the autoactivation of human cationic trypsinogen and activation peptide mutants. Wild-type and mutant trypsinogen were incubated at 1 μM with 10 nM initial trypsin in 0.1 M Tris-HCl (pH 8.0), 100 mM NaCl, and 0.05% Tween 20, at 37 °C, in the absence or presence of CaCl₂ (Ca²⁺) at the indicated concentrations. At given times 2 μL aliquots were removed and trypsin activity was determined as described in Experimental Procedures. Trypsin activity was expressed as percentage of the maximal activity in the presence of 10 mM CaCl₂. Representative experiments from two or three replicates are shown. Mutant K23_I24insIDK is denoted as insIDK.