Evaluation of the kinetic parameters of the activation of trypsinogen by trypsin

Kinetic analysis of the mechanism of trypsinogen activation by trypsin under rapid equilibrium conditions and certain relationships between the rate constants are presented. The kinetic equations are valid from the beginning of the reaction. In addition, we suggest a procedure, based on the above equations, for the evaluation of the kinetic parameters of the reaction. This procedure is applied to a set of experimental data collected during the activation of bovine trypsinogen by trypsin at 30 degrees C (pH 8.1) in 0.01 M CaCl2. In this system, the amount of active enzyme increases exponentially, as expected from an autocatalytic process. The apparent rate constant, delta, governing this increase would vary linearly with the trypsinogen concentration, [Z]0, if no Michaelis complex was detectable. However, the increase in delta with [Z]0 is clearly non-linear and fits a hyperbola (delta = k2[Z]0/(Kz + [Z]0)) well.