Kinetics of kappa-casein/chymosin hydrolysis

Kinetics of kappa-casein/chymosin hydrolysis was studied in pure kappa-casein and milk solutions at 7, 22, and 37 degrees C. The critical conversion for the reaction (X-c) decreased with increasing temperature in the milk solution. It was observed to be 0.86, 0.78, and 0.73 at 7, 22, and 37 degrees C, respectively. The Integrated Michaelis-Menten equation satisfactorily fitted to the experimental data. The Michaelis-Menten constant (K-M) was estimated to be 0.160 mu mol/ml, 0.105 mu mol/ml, 0.073 mu mol/ml at 7, 22, and 37 degrees C, respectively, in the milk solution. It was estimated to be 0.027 mu mol/ml in the kappa-casein solution in average within the given temperature range. The reaction rate constant (k(3)) was estimated to be 48.9 s(-1), 82.7 s(-1), and 177.3 s(-1) in the kappa-casein solution and 18.5 s(-1), 32.2 s(-1), and 64.9 s(-1) in the milk solution at 7, 22, and 37 degrees C, respectively. Effect of temperature on k(3) was expressed by Arrhenius equation in both solutions. The activation energy (E-a) was obtained to be 7376*10(-6) cal/mu mol in the kappa-casein solution and 7195*10(-6) cal/mu mol in the milk solution.