Figure 8.

Effect of replacement of Tyr²¹⁸ with Asp (Y218D, solid symbols) on the autoactivation of human anionic trypsinogen (wild type, open symbols). A. Autoactivation of 2 μM trypsinogen was initiated with 10 nM trypsin (final concentrations) and time-courses were followed at 37 °C in 0.1 M Na-HEPES (pH 7.0) and 10 mM CaCl₂. B. pH-dependence of autoactivation was determined as described in Experimental Procedures and in Fig 6B. Note that autoactivation experiments with anionic trypsinogen were always performed in 10 mM Ca²⁺ and in the absence of bovine serum albumin for maximal stability and activity [20].